JP5233201B2 - Magnetic device and frequency detector - Google Patents

Description

  The present invention relates to a magnetic device and a frequency detector.

  As a magnetoresistive effect element, a GMR (Giant Magnetoresistive) in which a nonmagnetic conductive layer is interposed between a fixed layer in which the magnetization direction is fixed and a magnetization free layer (free layer) in which the magnetization direction freely changes. Devices are known. As another magnetoresistive element, a TMR (Tunnel Magnetoresistive) element in which a nonmagnetic insulating layer is interposed between a fixed layer and a free layer is known. When a current is passed through these magnetoresistive effect elements, a spin-polarized current flows, and torque is generated by the interaction with the spin accumulated in the free layer. Depending on the polarity of the spin-polarized current, The direction of magnetization changes. In the free layer arranged in a constant magnetic field, even if an attempt is made to change the magnetization direction, torque acts on the magnetization direction so as to restore the stable direction constrained by the magnetic field. This movement in the direction of magnetization resembles that the weight of a pendulum pulled by gravity oscillates swaying with a specific force, and is called precession.

  In recent years, a phenomenon has been discovered in which resonance occurs when the natural frequency of precession in the direction of magnetization coincides with the frequency of the alternating current flowing in the free layer (see Non-Patent Document 1). The resistance value of the TMR element depends on the angle formed by the magnetization direction of the free layer and the magnetization direction of the fixed layer. When resonance of the magnetization direction occurs in the free layer, the magnetization direction of the free layer greatly oscillates, and the resistance value of the TMR element fluctuates greatly periodically. On the other hand, when the resistance value of the TMR element greatly fluctuates in synchronization with the input alternating current, the alternating current flowing between both ends of the TMR element fluctuates asymmetrically with respect to the zero level and has a direct current component. Minutes can be extracted as output (spin torque diode effect).

In order to cause the above-described phenomenon to occur in the TMR element, it is necessary to apply a magnetic field to the TMR element. Usually, the TMR element is placed in a magnetic field applying apparatus and an experiment is performed.
Nature, Vol.438, 17 November, 2005, pp.339-342

  However, while the phenomenon of the magnetoresistive effect element as described above is known, no magnetic device that can industrially use such a phenomenon is known, and application of discovery is expected.

  The present invention has been made in view of such problems, and an object thereof is to provide a magnetic device and a frequency detector that industrially utilize the resonance phenomenon of the magnetization direction of the magnetoresistive effect element.

  In order to solve the above-mentioned problems, a magnetic device according to the present invention is provided with a magnetoresistive effect element having a fixed layer and a free layer, so as to spontaneously generate a static magnetic field and to apply the static magnetic field to the free layer. And an input terminal for supplying an AC signal to the magnetoresistive effect element, and an output terminal for extracting an output voltage from the magnetoresistive effect element.

  According to the present invention, it is possible to obtain a magnetic device that industrially utilizes the resonance phenomenon of the magnetization direction of the magnetoresistive effect element. That is, when a current is passed through the magnetoresistive effect element described above, a spin-polarized current flows, and torque is generated by interaction with the spin accumulated in the free layer. Depending on the polarity of the spin-polarized current, the free layer The direction of magnetization changes. When the natural frequency of the magnetization direction of the free layer of the magnetoresistive element matches the frequency of the alternating current flowing through the magnetoresistive element, the vibration of the magnetization direction resonates, and the resistance value of the magnetoresistive element , The output voltage fluctuates asymmetrically with respect to the zero level and has a DC component. Here, the resonance frequency (natural frequency) depends on the magnitude of the magnetic field applied to the free layer. That is, the resonance frequency is determined depending on the magnitude of the static magnetic field applied to the free layer by the bias magnetic field application layer, and a signal having a specific frequency corresponding to the determined resonance frequency component among the input AC signals. Will have a direct current component by selectively fluctuating.

  In such a magnetic device, frequency detection and rectification of a high frequency signal is possible, and industrial application is possible. The bias magnetic field application layer is provided in place of a conventional large magnetic field application device, and uses a layer that spontaneously generates a static magnetic field. Therefore, no member other than the bias magnetic field application layer is required to generate the static magnetic field, and the magnetic device can be downsized.

  Furthermore, it is preferable that the AC signal flows in the stacking direction of the magnetoresistive effect elements. Thereby, the above-described resonance phenomenon can be easily generated.

  Furthermore, it is preferable that a pair of bias magnetic field application layers is provided so as to sandwich the free layer at a position separated from the free layer in the film surface direction of the magnetoresistive effect element. Thereby, since a uniform static magnetic field is formed between a pair of bias magnetic field application layers, it is possible to apply a bias magnetic field having a uniform intensity to the entire free layer between these layers. As a result, the operation of the magnetic device is stabilized.

  Further, the bias magnetic field application layer may be provided so as to be laminated with the magnetoresistive effect element at a position separated from the free layer in the laminating direction of the magnetoresistive effect element. In this case, since the magnetoresistive effect element and the bias magnetic field layer are stacked, the structure of the magnetic device is simplified.

  Further, it is preferable that the bias magnetic field application layer has residual magnetization and generates a static magnetic field by the residual magnetization. As a result, it is possible to apply a static magnetic field to the free layer simply by forming the bias magnetic field application layer with a material capable of having residual magnetization.

  The bias magnetic field application layer may include an antiferromagnetic layer and a ferromagnetic layer exchange coupled with the antiferromagnetic layer. In this case, when the antiferromagnetic layer and the ferromagnetic layer are viewed as one body, the bias magnetic field application layer is equivalent to having a residual magnetic field. This makes it possible to apply a static magnetic field to the free layer by the bias magnetic field application layer.

  Further, it is preferable that the direction of the static magnetic field applied by the bias magnetic field applying layer in the free layer and the direction of magnetization of the fixed layer intersect at an angle of 5 degrees or more in the film surface of the fixed layer. Thereby, the magnetization direction of the free layer is likely to vibrate. That is, the magnetization direction of the free layer matches the direction of the static magnetic field in the free layer. When a current is passed through the magnetoresistive effect element, the magnetization of the free layer receives torque in the same direction as or opposite to the magnetization direction of the fixed layer. For this reason, when the above-mentioned angles match, vibration in the magnetization direction of the free layer hardly occurs. If this angle is 5 degrees or more, vibration in the magnetization direction of the free layer can be easily generated.

  Furthermore, among the frequency components included in the AC signal, the frequency component corresponding to the natural frequency of the magnetization direction of the free layer, which depends on the magnitude of the static magnetic field applied to the free layer, and the magnetization direction of the free layer resonate. It is preferable to output a DC voltage by varying the frequency component corresponding to the natural frequency. As a result, if the magnetic device is manufactured so that the static magnetic field applied to the free layer has a predetermined magnitude, the DC voltage is changed by selectively changing the predetermined frequency component of the frequency components included in the AC signal. An output magnetic device can be obtained.

  Furthermore, it is preferable to have a plurality of magnetoresistive elements each having an independent output terminal and having different natural frequencies. As a result, when an AC signal includes a plurality of frequency components, a plurality of frequency components corresponding to a plurality of natural frequencies are varied, and a magnetic device that outputs a plurality of DC voltages corresponding to the frequency components is obtained. Can do.

  Furthermore, it is preferable to further include a signal generator for generating an AC signal. Thereby, the magnetic device which processes the signal which generate | occur | produces from a signal generator can be obtained.

  Furthermore, the signal generator is preferably an antenna. Thereby, the magnetic device which processes the signal received with the antenna can be obtained.

  A frequency detector according to the present invention includes any one of the magnetic devices described above and a monitor circuit that monitors a voltage output from an output terminal. According to the present invention, the voltage of a signal having a specific frequency among the input AC signals is detected by the monitor circuit. Therefore, this device functions as a frequency detector.

  Furthermore, it is preferable to further include a low-pass filter interposed between the monitor circuit and the magnetoresistive effect element. As a result, only the DC component from the magnetoresistive effect element can be transmitted and input to the monitor circuit. That is, since an AC signal is applied between both ends of the magnetoresistive effect element, by providing a low-pass filter, only a DC voltage of a signal having a specific frequency selectively varied among the AC signals can be extracted. .

  According to the magnetic device and the frequency detector of the present invention, it is possible to industrially use the resonance phenomenon of the magnetization direction of the free layer of the magnetoresistive effect element.

  Hereinafter, a magnetic device and a frequency detector according to embodiments will be described in detail with reference to the accompanying drawings. In addition, in each drawing, the same code | symbol is used for the same element and the overlapping description is abbreviate | omitted. In addition, the dimensional ratios in the components in the drawings and between the components are arbitrary for easy viewing of the drawings.

  FIG. 1 is a perspective view of a frequency detector 100 including a magnetic device 30 according to the present invention. In FIG. 1, the silicon substrate 10, the nonmagnetic insulating layer 16, and the protective layer 22, which will be described later, are omitted for easy understanding of the drawing (see FIG. 2).

  The magnetic device 30 receives an AC signal i between the magnetoresistive effect element 14, a pair of bias magnetic field application layers 18 provided to apply a static magnetic field to the magnetoresistive effect element 14, and both ends of the magnetoresistive effect element 14. A pair of input terminals INPUT1 and INPUT2 to be supplied and a pair of output terminals OUTPUT1 and OUTPUT2 for taking out the output voltage V across the magnetoresistive effect element 14 are provided. The input terminal INPUT2 and the output terminal OUTPUT2 are a reference terminal VREF and are connected to the ground.

  The stacking direction of the magnetoresistive effect element 14 is defined as a Z-axis direction, and two axes orthogonal to the Z-axis direction are defined as an X axis and a Y axis, respectively. A pair of bias magnetic fields with respect to the magnetoresistive effect element 14 so as to sandwich the magnetoresistive effect element 14 at a position separated in the X-axis direction which is one of the film surface directions (XY plane direction) of the magnetoresistive effect element 14 An application layer 18 is provided. The upper electrode layer 20 and the lower electrode layer 12 are in contact with both ends of the magnetoresistive effect element 14 in the Z-axis direction, and are electrically connected to the magnetoresistive effect element 14. The upper electrode layer 20 and the lower electrode layer 12 are plate-like electrodes having protrusions, and the magnetoresistive effect element 14 is disposed between the protrusions. The lower electrode layer 12 and the pair of bias magnetic field application layers 18 are separated from each other and are electrically insulated. Note that the terms “upper” and “lower” mean the position on the positive side and the negative side of the Z-axis, respectively, and are independent of the direction of gravity.

  A pair of upper electrode layer pads 28 and a lower electrode layer pad 24 are electrically connected to the upper electrode layer 20 and the lower electrode layer 12, respectively. A part of the upper electrode layer pad 28 and the lower electrode layer pad 24 is embedded in the protective layer 22 (not shown in FIG. 1; see FIG. 2), but in FIG. Of the upper electrode layer pad 28 and the lower electrode layer pad 24, a portion embedded in the protective layer 22 is indicated by a broken line.

  An AC signal i is applied from the signal source S between the one upper electrode layer pad 28 and the one lower electrode layer pad 24 via the input terminals INPUT1 and INPUT2. In order to prevent a direct current from being applied between one upper electrode layer pad 28 and one lower electrode layer pad 24, the wiring between one input terminal INPUT 1 and one upper electrode layer pad 28 has a capacitor C Are inserted in series.

  2 is an end view taken along line II-II in FIG. As shown in FIG. 2, the lower electrode layer 12, the magnetoresistive effect element 14, and the upper electrode layer 20 are laminated on the silicon substrate 10 in this order. The pair of bias magnetic field applying layers 18 are provided so as to sandwich the magnetoresistive effect element 14 at a position separated from the magnetoresistive effect element 14 in the X-axis direction. A nonmagnetic insulating layer 16 is provided between the pair of bias magnetic field application layers 18 and the magnetoresistive effect element 14 and between the pair of bias magnetic field application layers 18 and the lower electrode layer 12. Further, a protective layer 22 is formed so as to cover the upper electrode layer 20, the pair of bias magnetic field applying layers 18, and the nonmagnetic insulating layer 16.

  Details of the magnetoresistive effect element 14, the nonmagnetic insulating layer 16, and the pair of bias magnetic field applying layers 18 will be described with reference to FIGS. 3 is an enlarged end view in the vicinity of the magnetoresistive effect element 14 in FIG. 2, and FIG. 4 is an end view in the vicinity of the magnetoresistive effect element 14 along the line IV-IV in FIG.

  As shown in FIG. 3, the magnetoresistive effect element 14 is an element including the free layer 5. Specifically, the magnetoresistive element 14 includes an underlayer 1, an antiferromagnetic layer 2, and a lower ferromagnetic layer in which the magnetization direction 3AM is fixed in the Y-axis direction by exchange coupling with the antiferromagnetic layer 2. 3A, a nonmagnetic layer 3B made of a conductive metal such as Ru, and the magnetization direction 3CM through the nonmagnetic layer 3B are opposite to the magnetization direction 3AM of the lower ferromagnetic layer 3A (opposite to the Y axis). The fixed upper ferromagnetic layer 3C, the nonmagnetic layer 4, the free layer 5 made of a ferromagnetic material, and the cap layer 9 are stacked in this order. Here, the lower ferromagnetic layer 3A, the nonmagnetic layer 3B, and the upper ferromagnetic layer 3C form the fixed layer 3, and the magnetization direction of the fixed layer 3 is a free one of the two ferromagnetic layers of the fixed layer 3. The magnetization direction 3CM of the upper ferromagnetic layer 3C that is closer to the layer 5 is meant.

  When the magnetoresistive effect element 14 is composed of a TMR element, the nonmagnetic layer 4 is composed of a nonmagnetic insulating layer (tunnel barrier layer: suitable thickness 1 nm or less), and the magnetoresistive effect element 14 is a CPP (Current Perpendicular Plane). ) Type GMR element, the nonmagnetic layer 4 is made of a nonmagnetic conductive layer such as Cu. However, in any structure, the current flows in the stacking direction (Z-axis direction) of the magnetoresistive effect element 14. ).

Ferromagnetism is the magnetism of a substance that has adjacent spins aligned in the same direction and has a large magnetic moment as a whole, and a ferromagnet has spontaneous magnetization even in the absence of an external magnetic field. Materials that exhibit ferromagnetism at room temperature include Fe, Co, Ni, and Gd. As the ferromagnetic material, Co, Ni—Fe alloy, Co—Fe alloy, or the like can be preferably used. As the antiferromagnetic material constituting the antiferromagnetic layer 2, FeMn, IrMn, PtMn, NiMn and the like can be applied. When the nonmagnetic layer 4 is composed of an insulating layer for a TMR element, a tunnel barrier layer such as MgO, Al ₂ O ₃ or TiO having a thickness that causes a tunnel effect can be used as the insulating layer. The magnetoresistive effect element 14 may not include the underlayer 1 and the cap layer 9.

  The film thickness of the free layer 5 can be 1 to 10 nm, and the film thickness of the entire magnetoresistive element 14 can be 10 to 100 nm.

Then, a pair of bias magnetic field application layers 18 are provided so as to sandwich the free layer 5 at a position spaced apart from the magnetoresistive effect element 14 in the X axis. The bias magnetic field application layer is made of a hard magnetic material such as CoCrPt, and is magnetized so that the direction of the residual magnetization 18M1 is in the X-axis direction in FIG. Therefore, the bias magnetic field application layer 18 spontaneously generates a static magnetic field 18M2 in the X-axis direction of FIG. 3, and this static magnetic field 18M2 is applied to the free layer 5 as a bias magnetic field. As a result, the magnetization direction 5M of the free layer 5 is directed to the direction of the static magnetic field 18M2 in the free layer 5, that is, the X-axis direction. The thickness of the bias magnetic field applying layer 18 is the resonance frequency f ₀ as described later is adjusted to a predetermined value may be, for example, 1 to 100 nm.

  Further, as shown in FIG. 4 which is an end view taken along line IV-IV in FIG. 3, the direction of the static magnetic field 18M2 in the free layer 5 and the magnetization direction 3CM of the fixed layer 3 are the film surface of the fixed layer 3. In the present embodiment, the angle θ formed inside is 90 degrees.

  Next, operations of the magnetic device and the frequency detector will be described with reference to FIGS.

  When an alternating current i is supplied to the magnetoresistive effect element 14, spins having a specific polarity are injected into the free layer 5 of the magnetoresistive effect element 14, and the magnetization direction 5M of the free layer 5 changes according to the injection amount. To do. The magnetization direction 5M of the free layer 5 coincides with the direction in the free layer 5 of the static magnetic field 18M2 generated from the bias magnetic field application layer 18 when no alternating current is supplied. When polarized spin is injected into the free layer 5 from the fixed layer 3 side of the magnetoresistive effect element 14, a spin having a polarity in which the magnetization direction is aligned with the magnetization direction 3CM of the upper ferromagnetic layer 3C is the free layer. The free layer 5 receives a torque that rotates the magnetization direction 5M of the free layer 5 in a direction parallel to the magnetization direction 3CM of the upper ferromagnetic layer 3C. When electrons are injected into the free layer 5 in the opposite direction, spins having the same polarity as the magnetization direction 3CM of the upper ferromagnetic layer 3C are not injected into the free layer 5, so that the reverse of the above Polar spins are injected into the free layer 5, and the free layer 5 receives a torque that rotates the magnetization direction 5M of the free layer 5 in a direction antiparallel to the magnetization direction 3CM of the upper ferromagnetic layer 3C.

Since the polarity of the alternating current i changes with time, the magnetization direction of the free layer 5 is affected by the magnitude and frequency of the alternating current i and vibrates. When the natural frequency f _F of the magnetization direction 5M of the free layer 5 of the magnetoresistive effect element 14 matches the frequency f of the alternating current i flowing through the magnetoresistive effect element 14 (f ₀ = f _F = f), free The vibration of the magnetization direction 5M of the layer 5 resonates, the resistance value of the element of the magnetoresistive effect element 14 fluctuates rapidly, the voltage of the alternating current i fluctuates and has a direct current component,
The voltage is output as a voltage between output terminals OUTPUT1 and OUTPUT2 connected to the other upper electrode layer pad 28 and the other lower electrode layer pad 24, respectively.

The resonance frequency f ₀ increases depending on the magnitude of the static magnetic field 18M2 applied to the free layer 5 of the magnetoresistive effect element 14. The magnitude of the static magnetic field 18M2 depends on the material, film thickness, and the like of the bias magnetic field application layer 18. When adjusted these conditions increases the magnitude of the static magnetic field 18M2 and (18M2a <18M2b <18M2c), resonant (resonant) frequency _{f 0} is increased (see FIG. 5). That is, the material of the bias magnetic field applying layer 18, determines the resonance frequency f ₀ depending on the film thickness, etc., of the input AC signal (AC current i), corresponding to the determined component of the resonance frequency f ₀ The voltage V selectively fluctuates to have a DC component and appears between the output terminals OUTPUT1 and OUTPUT2 (see FIG. 6).

Further, the frequency detector 100 of the present embodiment includes a magnetic device 30 and further includes a monitor circuit 40 that monitors the voltage V output from the output terminals OUTPUT1 and OUTPUT2. When supplying an alternating current i to the magnetoresistive effect element 14, the voltage V of a specific resonant frequency corresponding to the natural frequency f _F of the free layer 5 is detected by the monitor circuit 40 (see FIG. 6). That is, it functions as a frequency detector that detects a specific frequency included in the AC signal i.

The frequency detector 100 further includes a low-pass filter L interposed between the monitor circuit 40 and the magnetoresistive effect element 14. This is because a pair of input terminals INPUT1 and INPUT2 and a pair of output terminals OUTPUT1 and OUTPUT2 are connected between both ends of the magnetoresistive effect element 14, but an AC signal i is applied to the input terminals INPUT1 and INPUT2. and for which, in order to take out only the selectively DC voltage V of a specific frequency of a signal voltage corresponding to the natural frequency _{f F} of the magnetization direction 5M of the free layer 5 from the output terminal OUTPUT1, OUTPUT2. The low-pass filter L transmits only the DC component from the magnetoresistive effect element 14 and inputs it to the monitor circuit 40. In this example, the low-pass filter L is composed of a coil interposed between the upper electrode layer pad 28 and the output terminal OUTPUT1.

  7 shows the relationship between the external magnetic field (Oe) and the output voltage (μV) when the TMR element is used as the magnetoresistive effect element 14 shown in FIG. 1, for each frequency (GHz) of the input high-frequency signal. FIG. 8 is a table showing the data of the graph of FIG. 7, and the numerical values in the table excluding the uppermost row and the leftmost column indicate the output voltage (μV).

  As is apparent from this graph, the magnitude of the external magnetic field corresponding to the resonance frequency exists, and it can be seen that the required external magnetic field increases as the frequency increases.

  In the present embodiment, an external magnetic field (static magnetic field 18M2 (see FIG. 3)) is applied to the free layer 5 by the bias magnetic field application layer 18, but this case can be considered similarly.

  Even when a CPP type GMR element is used in place of the TMR element, in consideration of the resonance principle of the spin vibration, the same action as the TMR element is performed according to the vibration of the magnetization direction. When a similar experiment was performed using a CPP type GMR element, the same result as in the case of the TMR element was obtained. That is, for example, when the applied voltage frequency is 4.5 GHz, the peak of the output voltage is observed at 4.5 GHz, and the voltage value exceeds 230 μV.

  Next, a method for manufacturing the magnetic device 30 according to the present embodiment will be described with reference to FIGS. 9A to 15A are plan views of an intermediate body of the magnetic device 30. FIG. 9-14 and FIGS. 15B and 15C are end views of the intermediate body of the magnetic device 30 along a predetermined line in the plan view A of each drawing.

  First, as shown in FIG. 9, a lower electrode layer 12 made of a conductive material such as Cu patterned in a predetermined shape is formed on a silicon substrate 10, and a magnetoresistive effect element 14 is formed on the entire surface. A patterned resist mask 15 is formed on the portion where the effect element 14 is to be left. Here, the lower electrode layer 12 and the magnetoresistive effect element 14 can be formed using, for example, a sputtering apparatus. Further, when the free layer 5 (not shown in FIG. 9; see FIG. 3) in the magnetoresistive effect element 14 is formed, the direction in which the static magnetic field 18M2 is applied in the future (the left and right directions in FIG. 9). ) May be formed while applying a magnetic field, and induced magnetic anisotropy may be imparted to the free layer 5 in that direction.

  Subsequently, as shown in FIG. 10, a portion of the magnetoresistive element 14 that is not masked by the resist mask 15 is removed by ion milling or the like. Thereby, the pattern of the magnetoresistive effect element 14 is formed.

Next, as shown in FIG. 11, a nonmagnetic insulating layer 16 such as SiO 2 is formed on the side surface of the magnetoresistive effect element 14 and the exposed surfaces of the lower electrode layer 12 and the silicon substrate 10. A pair of bias magnetic field application layers 18 patterned so as to be separated from the magnetoresistive effect element 14 are formed on both side surfaces of the first and second layers. Here, the nonmagnetic insulating layer 16 can be formed by a CVD apparatus using, for example, Si (OC ₂ H ₅ ) ₄ .

  Then, as shown in FIG. 12, after the protective layer 22a is formed on the entire surface, the surface is lapped by CMP or the like until the magnetoresistive effect element 14 and the bias magnetic field applying layer 18 are exposed, whereby the protective layer 22a is formed in the recess. And flatten the entire surface.

  Subsequently, as shown in FIG. 13, an upper electrode layer 20 made of a conductive material such as Cu patterned in a predetermined shape is formed so as to be in electrical contact with the magnetoresistive element 14.

  Next, as shown in FIG. 14, after the protective layer 22b is formed on the entire surface, the surface is lapped by CMP or the like to be flattened.

Then, as shown in FIG. 15, the surface of the protective layer 22 (= protective layer 22a + protective layer 22b) is masked with a resist except for areas where the upper electrode layer pad 28 and the lower electrode layer pad 24 will be formed in the future, The protective layer 22 in the unmasked region is removed by, for example, a reactive ion etching apparatus using C ₄ F ₈ or the like to form through holes reaching the upper electrode layer 20 and the lower electrode layer 12, and a sputtering apparatus or the like. Then, a conductive material such as Au is deposited to form a pair of upper electrode layer pad 28 and lower electrode layer pad 24.

  Thereafter, in order to fix the magnetization directions of the upper ferromagnetic layer 3C and the lower ferromagnetic layer 3A of the fixed layer 3, the magnetic layer is heated to about the blocking temperature of the antiferromagnetic layer 2 with a magnetic field applied in the Y-axis direction and then cooled. (See FIG. 3). After that, it is preferable to perform heating and cooling while applying a magnetic field in the X-axis direction, and to set the easy magnetization axis of the free layer 5 in the X-axis direction. At this time, in order not to change the magnetization direction 3CM of the fixed layer 3, the applied magnetic field is weakened and the heating temperature is lowered as compared with the case of the process for fixing the magnetization direction 3CM of the fixed layer 3 described above.

  As shown in FIG. 1, a pair of input terminals INPUT1 and INPUT2 are connected to one of a pair of upper electrode layer pads 28 and a lower electrode layer pad 24, and a pair of upper electrode layer pads 28 and a lower electrode layer are connected. The magnetic device 30 is completed by connecting the pair of output terminals OUTPUT1 and OUTPUT2 to the other of the pads 24 for use.

  If the resonance of the spin device is used by the magnetic device and the frequency detector according to the present embodiment as described above, frequency analysis in the GHz band that cannot be obtained by a normal Si semiconductor technology can be performed. We can expect development. The bias magnetic field application layer 18 is provided in place of a conventional large magnetic field application device, and uses a layer that spontaneously generates a static magnetic field 18M2. Therefore, no member other than the bias magnetic field application layer 18 is required to generate the static magnetic field 18M2, and thus the magnetic device 30 can be downsized.

  Further, in the magnetic device 30 of the present embodiment, an element of a type in which a current flows perpendicularly to the film surface is used as the magnetoresistive effect element 14. Therefore, the above-described resonance phenomenon can be preferably generated.

  In the magnetic device 30 of the present embodiment, a pair of bias magnetic field application layers 18 are provided so as to sandwich the free layer 5 at positions spaced from the free layer 5 in the film surface direction of the magnetoresistive effect element 14. ing. As a result, a uniform static magnetic field 18M2 is formed between the pair of bias magnetic field applying layers 18, so that a bias magnetic field having a uniform strength is applied to the entire free layer 5 between these layers. Can do. Therefore, the operation of the magnetic device 30 is stabilized.

  Further, in the magnetic device 30 of the present embodiment, the bias magnetic field application layer 18 has a remanent magnetization 18M1, and a remanent magnetization 18M1 generates a static magnetic field 18M2. Thereby, it is possible to apply the static magnetic field 18M2 to the free layer 5 only by forming the bias magnetic field application layer 18 with a material capable of having the residual magnetization 18M1.

  Further, in the magnetic device 30 of the present embodiment, the direction of the static magnetic field 18M2 applied by the bias magnetic field application layer 18 in the free layer 5 and the magnetization direction 3CM of the fixed layer 3 are the film surface of the fixed layer 3. The angle θ inside is 90 degrees. For this reason, the magnetization direction 5M of the free layer 5 is likely to vibrate. That is, the magnetization direction 5M of the free layer 5 coincides with the direction in the free layer 5 of the static magnetic field 18M2. When a current is passed through the magnetoresistive effect element 14, the magnetization of the free layer 5 receives torque so as to rotate in the same direction as the magnetization direction 3 CM of the fixed layer 3 or in the opposite direction. For this reason, when the above-mentioned angles coincide with each other, vibration in the magnetization direction 5M of the free layer 5 hardly occurs. In the present embodiment, since the angle θ is 90 degrees, vibration of the magnetization direction 5M of the free layer 5 can be easily generated.

In the magnetic device 30 of the present embodiment, the natural frequency f in the magnetization direction 5M of the free layer 5 that depends on the magnitude of the static magnetic field 18M2 applied to the free layer 5 among the frequency components included in the AC signal i. a frequency component corresponding to _F, and the resonance and the magnetization direction 5M of the free layer 5, and outputs the DC voltage V by varying the frequency component corresponding to the natural frequency f _F. For this reason, if the magnetic device 30 is manufactured so that the static magnetic field 18M2 applied to the free layer 5 has a predetermined magnitude, the predetermined frequency component of the frequency components included in the AC signal i is selectively changed. Thus, the magnetic device 30 that outputs a DC voltage is realized.

  The frequency detector 100 according to the present embodiment includes the above-described magnetic device 30 and a monitor circuit 40 that monitors voltages output from the pair of output terminals OUTPUT1 and OUTPUT2. For this reason, a frequency detector is realized in which the voltage of a signal having a specific frequency in the input AC signal i is detected by the monitor circuit 40.

  Further, the frequency detector 100 of the present embodiment further includes a low-pass filter L interposed between the monitor circuit 40 and the magnetoresistive effect element 14. Therefore, only the direct current component from the magnetoresistive effect element 14 can be transmitted and input to the monitor circuit 40. That is, since the AC signal i is applied between both ends of the magnetoresistive effect element 14, by providing the low-pass filter L, only the DC voltage of the signal having a specific frequency that has been selectively varied from the AC signal i can be obtained. It can be taken out.

  The present invention is not limited to the above embodiment, and various modifications can be made.

  In the above-described embodiment, the angle θ formed by the orientation of the static magnetic field 18M2 applied by the bias magnetic field application layer 18 in the free layer 5 and the magnetization direction 3CM of the fixed layer 3 in the film plane of the fixed layer 3. However, the angle θ may be an acute angle or an obtuse angle. This angle θ is preferably 5 degrees or more from the viewpoint of suitably causing the above-described resonance phenomenon.

  In the above-described embodiment, the bias magnetic field application layer 18 is formed of a hard magnetic material. However, it may be a two-layer structure of an antiferromagnetic layer and a ferromagnetic layer exchange-coupled to the antiferromagnetic layer. In this case, when the antiferromagnetic layer and the ferromagnetic layer are viewed as one body, it is equivalent to a single hard magnetic layer, and therefore the same effect as in the present embodiment can be obtained. In this case, the ferromagnetic layer may be a soft magnetic layer in addition to the hard magnetic layer.

  Further, as shown in FIG. 16, the fixed layer 3 of the magnetoresistive effect element 14a may be a single ferromagnetic layer. Also in this case, the same effect as the above embodiment can be obtained.

  In addition, as shown in FIG. 17, the bias magnetic field application layer 18 a may be laminated with the free layer 5 via the nonmagnetic layer 6. In other words, the bias magnetic field applying layer 18a may be laminated with the magnetoresistive effect element 14b at a position separated from the free layer 5 in the laminating direction of the magnetoresistive effect element 14b. The bias magnetic field applying layer 18a may be formed of a hard magnetic material.

  As a modification of the embodiment shown in FIG. 17, as shown in FIG. 18, the bias magnetic field applying layer 18b may have a two-layer structure including an antiferromagnetic layer 182b and a ferromagnetic layer 181b exchange-coupled thereto. Even in this case, when the antiferromagnetic layer 182b and the ferromagnetic layer 181b are viewed as one body, it is equivalent to the hard magnetic layer, and a bias magnetic field can be applied to the free layer 5.

  Moreover, the structure further provided as the signal source S with the signal generator for generating an alternating current signal is also possible. Thereby, the magnetic device which processes the signal which generate | occur | produces from a signal generator can be obtained. If a VCO (Voltage Controlled Oscillator) is used as the signal generator, it can be used as a transmitter. An antenna can also be used as the signal generator. In this case, a magnetic device that processes a signal received by the antenna can be obtained.

Further, as shown in FIG. 19, each independent output terminal OUTPUT1a, OUTPUT2a, OUTPUT1b, OUTPUT2b, OUTPUT1c, have OUTPUT2c, frequency detection having a plurality of magnetic devices 30a to natural frequency _{f F} are different, 30b, and 30c A vessel 100a is also possible. Here, the output terminals OUTPUT1a, OUTPUT1b, and OUTPUT1c correspond to the output terminal OUTPUT1 in the above-described embodiment, respectively, the output terminals OUTPUT2a, OUTPUT2b, and OUTPUT2c correspond to the output terminal OUTPUT2 in the above-described embodiment, respectively, and the magnetic device 30a. , 30b, and 30c correspond to the magnetic device 30 in the above-described embodiment (see FIG. 1). Thereby, when the AC signal i includes a plurality of frequency components, the plurality of frequency components corresponding to the plurality of natural frequencies f _F are varied, and the plurality of DC voltages Va, Vb, Vc are correspondingly changed. The frequency detector 100a which outputs each can be obtained. Here, the DC voltages Va, Vb, and Vc correspond to the DC voltage V in the above-described embodiment, and the frequency detector 100a corresponds to the frequency detector 100 in the above-described embodiment (see FIG. 1).

It is a perspective view of the frequency detector 100 provided with the magnetic device 30 which concerns on this invention. It is an end elevation along the II-II line in FIG. FIG. 3 is an enlarged end view near the magnetoresistive effect element 14 of FIG. 2. FIG. 4 is an end view taken along line IV-IV in FIG. 3. It is a graph which shows the relationship between the frequency f of the alternating current i, and the output voltage V. It is a graph which shows the relationship between the magnetic field H and the voltage V. FIG. 1 is a graph showing the relationship between an external magnetic field (Oe) and an output voltage (μV) when a TMR element is used as the magnetoresistive element 14 shown in FIG. 1 for each frequency (GHz) of an input high-frequency signal. is there. It is a table | surface which shows the data of the graph of FIG. 2 is a plan view and an end view of an intermediate body of the magnetic device 30. FIG. 2 is a plan view and an end view of an intermediate body of the magnetic device 30. FIG. 2 is a plan view and an end view of an intermediate body of the magnetic device 30. FIG. 2 is a plan view and an end view of an intermediate body of the magnetic device 30. FIG. 2 is a plan view and an end view of an intermediate body of the magnetic device 30. FIG. 2 is a plan view and an end view of an intermediate body of the magnetic device 30. FIG. 2 is a plan view and an end view of an intermediate body of the magnetic device 30. FIG. It is an end elevation which shows the modification of embodiment. It is an end elevation which shows the modification of embodiment. It is an end elevation which shows the modification of embodiment. It is an end elevation which shows the modification of embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Fixed layer, 3CM ... Magnetization direction of fixed layer, 5 ... Free layer, 14 ... Magnetoresistive element, 18 ... Bias magnetic field application layer, 18M2 ... Static magnetic field, INPUT1 , INPUT2... Input terminal, OUTPUT1, OUTPUT2.

Claims (12)

A magnetoresistive effect element having a fixed layer and a free layer;
A bias magnetic field application layer provided so as to spontaneously generate a static magnetic field and to apply the static magnetic field to the free layer;
An input terminal for supplying an AC signal to the magnetoresistive element;
An output terminal for extracting an output voltage from the magnetoresistive element;
Equipped with a,
Among the frequency components included in the AC signal, the frequency component corresponding to the natural frequency of the magnetization direction of the free layer depending on the magnitude of the static magnetic field applied to the free layer, and the magnetization direction of the free layer Resonate,
A magnetic device that outputs a DC voltage by varying a frequency component corresponding to the natural frequency .   The magnetic device according to claim 1, wherein the AC signal flows in a stacking direction of the magnetoresistive effect elements.   3. The bias magnetic field application layer is provided in a pair so as to sandwich the free layer at a position spaced apart from the free layer in the film surface direction of the magnetoresistive element. The magnetic device described in 1.   The bias magnetic field application layer is provided so as to be laminated with the magnetoresistive effect element at a position separated from the free layer in the lamination direction of the magnetoresistive effect element. The magnetic device described in 1.   5. The magnetic device according to claim 1, wherein the bias magnetic field application layer has a remanent magnetization and generates the static magnetic field by the remanent magnetization.   5. The magnetic device according to claim 1, wherein the bias magnetic field application layer includes an antiferromagnetic layer and a ferromagnetic layer exchange-coupled to the antiferromagnetic layer. .   The direction of the static magnetic field applied by the bias magnetic field application layer in the free layer and the direction of magnetization of the fixed layer intersect at an angle of 5 degrees or more in the film surface of the fixed layer. The magnetic device according to claim 1. Have respective separate said output terminal, a magnetic device according to any one of claims 1 to 7, wherein the natural frequency and having a plurality of different magneto-resistive element, respectively. The magnetic device according to any one of claims 1 to 8, further comprising a signal generator for generating the AC signal. The magnetic device according to claim 9 , wherein the signal generator is an antenna. The magnetic device according to any one of claims 1 to 10 ,
A monitor circuit for monitoring the voltage output from the output terminal;
A frequency detector comprising: The frequency detector according to claim 11 , further comprising a low pass filter interposed between the monitor circuit and the magnetoresistive effect element.

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