JP2014059943A - Perpendicular magnetic recording medium, magnetic storage device, and method for manufacturing perpendicular magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a perpendicular magnetic recording medium or the like capable of being formed in a short time by using an inexpensive material.SOLUTION: A soft magnetic layer 12 is laminated on a substrate 11, and a shield layer 13 is formed by forming a single crystal film or a highly oriented film of a magnesium oxide being a cubic crystal having grating constant which is a little larger than 1/2 of the grating constant of cobalt ferrite on the laminated soft magnetic layer. On a (001) crystal surface of the magnesium oxide, high frequency magnetron sputtering is performed in which oxygen is used as reactive gas and an iron cobalt alloy is used as a target metal, and a perpendicular magnetic recording layer 14 is formed by growing the single crystal film or the highly oriented film of cobalt ferrite.

Description

  The present invention relates to a perpendicular magnetic recording medium, a magnetic storage device, and a method for manufacturing a perpendicular magnetic recording medium.

  With the recent development of information processing technology, it is required to improve the recording density of magnetic recording media, improve the stability of magnetic recording, etc., but magnetic recording media adopting the perpendicular magnetic recording method that meets these requirements have been developed Have been commercialized. Cobalt chromium platinum (CoCrPt) alloy or the like is used as a material for the perpendicular magnetic recording layer of the current perpendicular magnetic recording system. In the near future, it has been studied to use an iron platinum (FePt) alloy having a larger magnetic anisotropy for thermal assist recording (for example, cited documents 1 and 2).

  The cobalt chromium platinum alloy and the iron platinum alloy used for the perpendicular magnetic recording layer are both expensive because platinum, which is a rare metal, is used. Furthermore, these resources are unevenly distributed on the earth, and it may be difficult to obtain resources due to the global situation.

On the other hand, the inventors of the present application have disclosed a perpendicular magnetic recording medium and a magnetic memory using inexpensive cobalt ferrite (CoFe ₂ O ₄ ), which is known for its large magnetic anisotropy, as a perpendicular magnetic recording layer. An application has been filed for an invention relating to a device (Patent Document 3).

JP 2004-79058 A JP 2008-176923 A JP 2011-60346 A

In Patent Document 3, cobalt ferrite (CoFe ₂ O ₄ ) is grown on a 001 crystal plane of magnesium oxide by molecular beam epitaxy using pure ozone as an oxidation source and iron and cobalt as raw materials. A perpendicular magnetic recording layer made of a single crystal film is produced. The inventors have confirmed high perpendicular magnetic anisotropy for the perpendicular magnetic recording layer grown by this method.

  By forming this perpendicular magnetic recording layer on the soft magnetic backing layer, a perpendicular magnetic recording medium can be produced without using a rare metal such as platinum.

  However, since the cobalt ferrite crystal growth by molecular beam epitaxy described in Patent Document 3 takes a long time and is not suitable for mass production, it is cost-effective enough to replace a perpendicular magnetic recording layer using platinum so far. There was no.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a perpendicular magnetic recording medium and the like that can be produced in a short time using an inexpensive material.

In order to achieve the above object, a perpendicular magnetic recording medium according to the first aspect of the present invention provides:
001 crystal plane of a seed layer made of a cubic crystal having a lattice constant larger than 1 / n (n is a natural number) of cobalt ferrite and having a lattice mismatch within a predetermined range with respect to the 001 crystal plane of the cobalt ferrite. In contrast, by performing reactive sputtering using oxygen as a reactive gas and iron cobalt alloy as a target metal, and having a perpendicular magnetic recording layer formed by growing a single crystal film or a highly oriented film of cobalt ferrite,
It is characterized by that.

  The seed layer may include magnesium oxide or titanium nitride.

  The reactive sputtering may be radio frequency magnetron sputtering or DC pulse magnetron sputtering.

  The reactive sputtering may be planar sputtering in which an iron cobalt alloy is disposed at a position facing the 001 crystal plane of the seed layer.

  The temperature at which the perpendicular magnetic recording medium is generated during the reactive sputtering may be 600 ° C. or higher.

A first soft magnetic layer made of an oxide having a spinel-type or inverse spinel-type ionic crystal structure; and a second soft magnetic layer made of a single metal having ferromagnetism or an alloy containing a single metal having ferromagnetism; A soft magnetic backing layer comprising
The seed layer may be laminated on a surface of the second soft magnetic layer opposite to the first soft magnetic layer.

The oxide is an oxide containing triiron tetroxide or maghemite, the metal is iron, and the alloy containing the metal is an alloy containing iron,
The soft magnetic backing layer may further include a nonmagnetic layer made of an insulator between the first soft magnetic layer and the second soft magnetic layer.

  A magnetic storage device according to a second aspect of the present invention includes the perpendicular magnetic recording medium according to the first aspect and a head that records or reproduces information on the perpendicular magnetic recording medium. It is characterized by that.

A method for manufacturing a perpendicular magnetic recording medium according to the third aspect of the present invention includes:
A method of manufacturing a perpendicular magnetic recording medium having a perpendicular magnetic recording layer made of cobalt ferrite,
001 crystal of a seed layer made of a cubic crystal having a lattice constant larger than 1 / n (n is a natural number) of the cobalt ferrite and having a lattice mismatch with respect to the 001 crystal plane of the cobalt ferrite within a predetermined range. Reactive sputtering using oxygen as a reactive gas and an iron cobalt alloy as a target metal is performed on the surface to grow the single crystal film or highly oriented film of cobalt ferrite, thereby forming the perpendicular magnetic recording layer Having steps,
It is characterized by that.

The seed layer includes magnesium oxide;
You may make it further have the process of producing | generating a seed layer by forming a magnesium oxide thin film so that the 001 crystal plane of the magnesium oxide may orientate on the surface of the seed layer.

The seed layer includes magnesium oxide and titanium nitride,
After forming a magnesium oxide thin film so that the 001 crystal plane of the magnesium oxide is oriented on the surface, the titanium nitride is deposited on the 001 crystal plane of the magnesium oxide, thereby forming the titanium nitride on the surface of the seed layer. You may make it further have the process of producing | generating a seed layer so that the 001 crystal plane may be orientated.

  The reactive sputtering may be RF magnetron sputtering or DC pulse magnetron sputtering.

  The reactive sputtering may be planar sputtering in which an iron cobalt alloy is disposed at a position facing the 001 crystal plane of the seed layer.

  The temperature at which the perpendicular magnetic recording medium is generated during the reactive sputtering may be 600 ° C. or higher.

Producing a first soft magnetic layer made of an oxide having a spinel-type or inverse spinel-type ionic crystal structure;
Forming a nonmagnetic layer made of an insulator on the first soft magnetic layer;
Producing a second soft magnetic layer made of a metal having ferromagnetic property alone or an alloy containing a metal having ferromagnetic property alone on the non-magnetic layer, and
The seed layer may be formed on the second soft magnetic layer.

  The oxide may be an oxide containing triiron tetroxide or maghemite, the insulator may be magnesium oxide, the metal may be iron, and the alloy containing the metal may be an alloy containing iron.

  According to the present invention, it is possible to provide a perpendicular magnetic recording medium or the like that can be produced using an inexpensive material in a short time.

1 is an external view of a perpendicular magnetic recording medium and a recording / reproducing head according to Embodiment 1. FIG. 1 is a cross-sectional view of a perpendicular magnetic recording medium according to Embodiment 1. FIG. It is a figure for demonstrating the crystal structure of cobalt ferrite. 6 is a diagram for explaining a method of manufacturing the perpendicular magnetic recording medium according to Embodiment 1. FIG. (A) is a figure which shows the change of the magnetization curve when changing the temperature of a board | substrate, (b) is a figure which shows the change of the magnetization curve when changing the film thickness of a perpendicular magnetic recording layer. 1 is an external view of a magnetic storage device according to an embodiment. 6 is a cross-sectional view of a perpendicular magnetic recording medium according to Embodiment 2. FIG. 6 is a cross-sectional view of a perpendicular magnetic recording medium according to Embodiment 3. FIG. FIG. 6 is an external view of a perpendicular magnetic recording medium and a recording / reproducing head according to Embodiment 3.

(Embodiment 1)
Embodiment 1 of the present invention will be described in detail with reference to FIGS.

  As shown in FIGS. 1 and 2, the perpendicular magnetic recording medium 10 according to the present embodiment includes a substrate 11, a soft magnetic layer 12, a seed layer 13, and a perpendicular magnetic recording layer 14.

  When writing magnetic information on the perpendicular magnetic recording medium 10, as shown in FIG. 1, a current flows through the write head 51 of the recording / reproducing head 50, so that the lines of magnetic force emitted from the main pole 511 of the write head 51 After passing through the perpendicular magnetic recording layer 14 and the seed layer 13 and passing through the soft magnetic layer 12, the seed layer 13 and the perpendicular magnetic recording layer 14 are penetrated to return to the return pole 512 of the write head 51. At this time, the magnetic flux density of the magnetic lines immediately after coming out of the main pole 511 is high, and the magnetic flux density of the magnetic lines just before returning to the return pole 512 is low. Therefore, magnetization reversal occurs in the perpendicular magnetic recording layer 14 below the main pole 511, Magnetically recorded.

  When reading the magnetic information recorded on the perpendicular magnetic recording medium 10, the reading head 52 detects the magnetic flux in each recording bit of the perpendicular magnetic recording layer 14.

  The substrate 11 of the perpendicular magnetic recording medium 10 is made of a nonmagnetic material, such as a glass substrate or a silicon substrate. The soft magnetic layer 12 is made of a material having a small coercive force and a high magnetic permeability, and is made of, for example, iron. In the present embodiment, a case where the soft magnetic layer 12 is made of an iron film will be described.

  The seed layer 13 is composed of a single crystal film or highly oriented film of magnesium oxide (MgO), and the 001 crystal plane of magnesium oxide is oriented on the boundary surface of the seed layer 13 on the perpendicular magnetic recording layer 14 side. Here, the highly oriented film is a crystal film having a high crystal axis orientation and a function equivalent to that of a single crystal film in terms of the function of the film.

The perpendicular magnetic recording layer 14 is composed of a single crystal film or a highly oriented film of cobalt ferrite (Co _X Fe _{3 -X} O ₄ ). Cobalt ferrite is a spinel oxide known as a material having a large magnetic anisotropy and a high coercive force.

  By growing a cobalt ferrite single crystal film or a highly oriented film on the 001 crystal plane of magnesium oxide, the 001 crystal plane of cobalt ferrite can be oriented on the surface 101 of the perpendicular magnetic recording medium 10. As a result, the cobalt ferrite of the perpendicular magnetic recording layer 14 has a magnetic anisotropy in a direction perpendicular to the surface 101 of the perpendicular magnetic recording medium 10.

Here, the value of X of cobalt ferrite (Co _X Fe _{3 -X} O ₄ ) is an arbitrary number less than 3, but according to the size of perpendicular magnetic anisotropy required for the perpendicular magnetic recording layer 14 Optimized. In this embodiment, for example, cobalt ferrite (CoFe ₂ O ₄ ) with X = 1 constitutes the perpendicular magnetic recording layer 14.

As shown in FIG. 3, the single crystal of cobalt ferrite (Co _X Fe _{3 -X} O ₄ ) has a structure in which a cobalt atom and an iron atom are contained in a 4-coordinate site A and a 6-coordinate site B. It has a dimensionally adjacent crystal structure and the unit cell size is about 0.838 nm. The ratio of the number of cobalt atoms to the number of iron atoms is X: 3-X.

  Here, the unit cell size of a single crystal of magnesium oxide (MgO) which is a cubic crystal is about 0.424 nm, which is larger than ½ of the unit cell size of a single crystal of cobalt ferrite and has a lattice mismatch degree. About -1%. Here, the lattice mismatch degree f is defined by the following equation. In the following formula (1), a is a lattice constant of the material of the seed layer 13, b is a lattice constant of the material of the perpendicular magnetic recording layer 14, and n is an arbitrary natural number. In the present embodiment, n is 2 because the lattice constant of cobalt ferrite is about twice the lattice constant of magnesium oxide.

  f = (b−n · a) / (n · a) (1)

  In other words, since the lattice constant of magnesium oxide is slightly larger than 1/2 of the lattice constant of cobalt ferrite, tensile stress acts on the film surface of cobalt ferrite at the interface between magnesium oxide and cobalt ferrite, and the magnetic properties of cobalt ferrite. Perpendicular magnetic anisotropy appears due to the elastic effect. In addition, since the degree of crystal mismatch is sufficiently small, a single crystal film or a highly oriented film of cobalt ferrite can be stably grown on the 001 crystal plane of magnesium oxide.

  Next, a method for manufacturing the perpendicular magnetic recording medium 10 will be described.

  First, an iron film of the soft magnetic layer 12 is formed on the substrate 11. The deposition method of the iron film may be a well-known vapor deposition method or sputtering method. Thereafter, magnesium oxide is deposited on the iron film in a polycrystalline or amorphous state by using a vapor deposition method or a sputtering method, and then annealed to orient the 001 crystal plane of the magnesium oxide on the surface of the seed layer 13. .

  A method of forming a cobalt ferrite single crystal film or highly oriented film on the 001 crystal plane of magnesium oxide will be described in detail with reference to FIG.

  The sputtering apparatus 20 is an apparatus capable of generating plasma by helicon waves and performing high-frequency magnetron sputtering, for example, and includes a sample stage 22, a magnet 23, and a high-frequency power source 24 in a chamber 21. The apparatus further includes an oxygen gas generator 25 for introducing oxygen into the chamber 21, a variable leak valve 26, and a nozzle 27.

  A sample table 22 is provided with a substrate 11, a soft magnetic layer 12, and a seed layer 13 stacked thereon. A target metal 28 is installed along the magnet 23, and the target metal 28 is arranged to face the sample stage 22. That is, a planar method is employed in which the target metal 28 is arranged in a direction perpendicular to the direction of crystal growth by sputtering. The planar method is suitable for mass production because the film forming speed is high.

  The target metal 28 is a cobalt iron alloy, and the alloy composition ratio is adjusted so that the composition ratio of cobalt and iron in the generated cobalt ferrite is X: 3-X.

  Argon gas is introduced into the chamber 21, and the argon gas enters a plasma state when voltage is applied by the high frequency power supply 24, the argon ions collide with the target metal 28, and cobalt atoms and iron atoms are blown to the sample side. Deposited on the 001 crystal plane of magnesium oxide. At this time, since oxygen introduced from the nozzle 27 is reacted as a reactive gas on the substrate, a single crystal film or a highly oriented film of cobalt ferrite is formed on the 001 crystal plane of magnesium oxide. That is, the sputtering method here is a reactive sputtering method using oxygen as a reactive gas.

  Here, when oxygen is introduced into the chamber 21, the surface of the target metal 28 is oxidized. Since a high frequency voltage is applied to the target metal 28, argon ions and electrons are applied to the surface of the target metal 28. Can be prevented, and sputtering can be performed efficiently.

  Such sputtering is continued until the cobalt ferrite has a predetermined thickness, and the perpendicular magnetic recording layer 14 is formed.

  The magnetic characteristics of the perpendicular magnetic recording layer 14 of the perpendicular magnetic recording medium 10 manufactured by the above method were evaluated. For the experiment, magnetic measurements were performed on RF magnesiumtron sputtering using oxygen gas as a reactive gas on a magnesium oxide hexkai substrate having a length of 10 mm and a width of 20 mm.

  The perpendicular magnetic recording layer 14 was formed by changing the temperature at which the perpendicular magnetic recording medium 10 was produced at the time of sputtering, that is, the temperature closest to the hekikai substrate, in the range of 300 to 630 ° C. Here, the temperature at the production location of the perpendicular magnetic recording medium 10 is the indicated temperature of the heater obtained by measuring the temperature in the vicinity of the heater installed on the back surface of the hekikai substrate with a thermocouple.

  Other sputtering conditions were such that the pressure after introducing oxygen into the chamber 21 was 0.6 Pa, and the RF power was 100 W. Hereinafter, the evaluation results will be described.

  Evaluation was made on cobalt ferrite with x = 0.75 and a film thickness of 60 to 100 nm. The evaluation result will be described with reference to FIG. In FIG. 5, the horizontal axis represents external magnetization, and the vertical axis represents magnetic flux density.

  FIG. 5A shows a magnetization curve (hysteresis loop) in the perpendicular direction of the perpendicular magnetic recording layer 14 made of cobalt ferrite having x = 0.75 and a film thickness of 67 nm. As can be seen from FIG. 5A, the magnetization curve changes depending on the temperature closest to the hekikai substrate during sputtering, that is, the temperature at which the perpendicular magnetic recording medium 10 is generated. The saturation magnetization is the largest when the temperature near the Hekikai substrate is 600 ° C., and the hysteresis of the magnetization curve is also square. The ratio Mr / Ms between the residual magnetization Mr and the saturation magnetization Ms is 0.85, which is close to 1.

  Further, FIG. 5B shows magnetization curves when the thickness of the perpendicular magnetic recording layer 14 is 67 nm and when it is 100 nm. The immediate temperature of the substrate was 600 ° C. As can be seen from FIG. 5B, the hysteresis of the magnetization curve when the film thickness is 100 nm is more square than the film thickness of 67 nm. The ratio Mr / Ms between the remanent magnetization Mr and the saturation magnetization Ms was 0.95, which was further closer to 1. It can be said that the hysteresis of the magnetization curve when the temperature is 600 ° C. and the film thickness is 100 nm is a sufficient characteristic as a magnetic material for a recording medium.

Further, it can be seen that the saturation magnetization Ms is about 400 [emu / cc] and has a value corresponding to the bulk body. Moreover, the coercive force calculated from the hysteresis loop of the magnetization curve in FIG. 5A was 20 kOe. The magnitude of perpendicular magnetic anisotropy calculated by magnetic measurement was about 1 × 10 ⁷ erg / cm ³ for each cobalt ferrite with x = 0.75 and a film thickness of 60 to 100 nm.

Here, the value of X of cobalt ferrite _{(Co X Fe 3-X O} 4) was evaluated for the case of 0.75, the vertical magnetic anisotropy by controlling the ratio of cobalt by increasing or decreasing the value of X The magnitude of directionality can be tuned.

  From the above evaluation results, the perpendicular magnetic recording layer 14 having a square magnetization curve can be manufactured by raising the temperature of the production location of the perpendicular magnetic recording medium 10 during sputtering to 600 ° C. or higher. The temperature of the sputtering apparatus used in this experiment only rises up to 630 ° C, and no higher temperature was measured. However, when the temperature exceeded 650 ° C, the cobalt ferrite crystal structure collapsed and perpendicular magnetic anomalies were observed. A temperature of 650 ° C. or higher is not desirable because the directionality deteriorates.

  The perpendicular magnetic recording medium 10 provided with the perpendicular magnetic recording layer 14 having the above magnetic characteristics is incorporated in a magnetic storage device 1 as shown in FIG. 6, for example. The magnetic storage device 1 includes a perpendicular magnetic recording medium 10, a recording / reproducing head 50, a housing 73, a hub 75, a suspension 78, and an arm 79. The perpendicular magnetic recording medium 10 is attached to a hub 75 that is rotated by a motor or the like.

  The recording / reproducing head 50 is a composite recording / reproducing head including a reading head 52 such as an MR (Magneto Resistive) head or a GMR (Giant Magneto Resistive) head and a writing head 51 such as an inductive head. The recording / reproducing head 50 is attached to the tip of an arm 79 via a suspension 78. A plurality of the perpendicular magnetic recording media 10 may be connected to the hub 75 with an appropriate separation, and a recording / reproducing head 50, a suspension 78, and an arm 79 may be provided for each perpendicular magnetic recording medium 10.

  As described above, in this embodiment, oxygen is used as a reactive gas with respect to the 001 crystal plane of magnesium oxide having cubic lattice constant slightly larger than 1/2 of the lattice constant of cobalt ferrite. Reactive sputtering using an iron-cobalt alloy as the target metal 28 is performed to grow a single crystal film or highly oriented film of cobalt ferrite, thereby forming a seed layer 13 made of magnesium oxide and a perpendicular magnetic recording layer 14 made of cobalt ferrite. Thus, the perpendicular magnetic recording medium 10 was manufactured. Thereby, a perpendicular magnetic recording medium composed of an inexpensive material called cobalt ferrite can be manufactured in a short time.

(Embodiment 2)
The second embodiment of the present invention will be described in detail with reference to FIG.

  The perpendicular magnetic recording medium 30 according to the present embodiment includes a substrate 11, a soft magnetic layer 12, a seed layer 13, and a perpendicular magnetic recording layer 14 as in the first embodiment, but the configuration of the seed layer 13 is implemented. Different from Form 1. As shown in FIG. 7, the seed layer 13 includes a first layer 131 made of a magnesium oxide (MgO) single crystal film or a highly oriented film, and a second layer made of titanium nitride (TiN) single crystal film or a highly oriented film. It is composed of layer 132.

  The unit cell size of the cubic single crystal of magnesium oxide and titanium nitride is 0.424 nm, which is slightly larger than ½ of the unit cell size of cobalt ferrite. A single crystal film or highly oriented film of ferrite can be stably grown and perpendicular magnetic anisotropy can be expressed in cobalt ferrite.

  A method for manufacturing the perpendicular magnetic recording medium 30 according to the present embodiment will be described.

  First, an iron film of the soft magnetic layer 12 is formed on the substrate 11. The deposition method of the iron film may be a well-known vapor deposition method or sputtering method. Thereafter, magnesium oxide is thinly deposited in a polycrystalline or amorphous state on the iron film by a vapor deposition method, a sputtering method, or the like, and then an annealing process is performed to orient the 001 crystal plane of magnesium oxide on the surface of the first layer 131.

  Thereafter, a single crystal film or highly oriented film of titanium nitride is grown on the 001 crystal plane of magnesium oxide by vapor deposition or sputtering. Thereby, the seed layer 13 in which the 001 crystal plane of titanium nitride is oriented on the surface of the second layer 132, that is, the surface of the seed layer 13, can be generated. Here, since the film formation rate of titanium nitride is faster than that of magnesium oxide, the case where the seed layer 13 is composed of magnesium oxide and titanium nitride is manufactured rather than the case where the seed layer 13 is composed of magnesium oxide alone. Time can be shortened.

  A perpendicular magnetic recording layer 14 made of cobalt ferrite is formed on the 001 crystal plane of titanium nitride of the seed layer 13 thus formed. The cobalt ferrite film forming method is the same as in the first embodiment.

  As described above, in this embodiment, titanium nitride is formed on the 001 crystal plane of magnesium oxide having cubic lattice constant slightly larger than 1/2 of the lattice constant of cobalt ferrite. The perpendicular magnetic recording layer 14 was formed on the 001 crystal plane of titanium nitride. Thereby, the generation time of the seed layer 13 can be shortened, and the perpendicular magnetic recording medium 30 can be manufactured in a shorter time.

(Embodiment 3)
A third embodiment of the present invention will be described in detail with reference to FIGS.

  As shown in FIG. 8, the perpendicular magnetic recording medium 40 according to the present embodiment includes a substrate 11, a soft magnetic backing layer 41, a seed layer 13, and a perpendicular magnetic recording layer 14. The soft magnetic backing layer 41 includes a first soft magnetic layer 411, a nonmagnetic layer 412, and a second soft magnetic layer 413.

  The nonmagnetic layer 412 functions as an antiferromagnetic interlayer coupling layer, and couples the remanent magnetization of the second soft magnetic layer 413 generated by recording on the perpendicular magnetic recording layer 14 with the antiparallel magnetization of the first soft magnetic layer 411. . By this antiferromagnetic interlayer coupling, macroscopic magnetic flux can be canceled to prevent the magnetic head from reaching the reading head 52, and spike noise during reading of the recorded magnetization can be suppressed (FIG. 9).

Here, the first soft magnetic layer 411 is an oxide layer having a spinel type or inverse spinel type ionic crystal structure, for example, maghemite (γ-Fe ₂ O ₃ ) or triiron tetroxide (Fe ₅ O ₄ ). Consists of The nonmagnetic layer 412 is an insulator layer and is made of, for example, magnesium oxide (MgO). The second soft magnetic layer 413 is a metal layer and is made of, for example, iron (Fe). These layers do not use a conventional rare material such as ruthenium or platinum, but are made of an inexpensive material, which can contribute to further cost reduction of the perpendicular magnetic recording medium 40.

  A method for manufacturing the perpendicular magnetic recording medium 40 according to the present embodiment will be described.

First, an oxide film of the first soft magnetic layer 411 is formed on the substrate 11. When the first soft magnetic layer 411 is composed of triiron tetroxide (Fe ₅ O ₄ ), the first soft magnetic layer 411 is formed by reactive deposition or reactive sputtering of iron using a pure oxygen gas as a reactive gas. When the magnetic layer 411 is composed of maghemite (γ-Fe ₂ O ₃ ), it is formed by reactive deposition or reactive sputtering of iron using pure ozone gas as a reactive gas.

  Thereafter, magnesium oxide and iron are sequentially formed. The film formation method of magnesium oxide and iron is a well-known vapor deposition method or sputtering method.

  Thereafter, a seed layer 13 made of magnesium oxide is generated. Specifically, magnesium oxide is deposited in a polycrystalline or amorphous state by an evaporation method or a sputtering method, and then an annealing process is performed to orient the 001 crystal plane of magnesium oxide on the surface of the seed layer 13.

  The perpendicular magnetic recording layer 14 made of cobalt ferrite is formed on the 001 crystal plane of the magnesium oxide of the seed layer 13, and the method of forming the cobalt ferrite is the same as in the first embodiment.

  As described above, in the present embodiment, the first soft magnetic layer 411 made of a spinel or reverse spinel oxide film, the nonmagnetic layer 412 made of an insulator, and the second soft magnetic layer 413 made of a metal film. The perpendicular magnetic recording medium 40 is manufactured by laminating the seed layer 13 made of magnesium oxide and the perpendicular magnetic recording layer 14 made of cobalt ferrite on the soft magnetic backing layer 41 laminated in order. . Thereby, in the perpendicular magnetic recording medium 40 made of an inexpensive material, spike noise at the time of reading the recording magnetization can be suppressed.

  Thus, the present invention is a cubic crystal having a lattice constant larger than 1 / n (n is a natural number) of cobalt ferrite and having a lattice mismatch with respect to the 001 crystal plane of the cobalt ferrite within a predetermined range. The 001 crystal plane of the seed layer is subjected to reactive sputtering using oxygen as a reactive gas and an iron-cobalt alloy as a target metal to grow a single crystal film or a highly oriented film of the cobalt ferrite, thereby generating perpendicular magnetism. A recording layer was formed. Thereby, a perpendicular magnetic recording medium composed of an inexpensive material can be provided in a short time.

  In addition, this invention is not limited to the said embodiment, Of course, the various change in the range which does not deviate from the summary of this invention is possible.

  For example, in the above embodiment, only one surface of one perpendicular magnetic recording medium is used for magnetic recording. However, a perpendicular magnetic recording layer may be formed on both surfaces and both surfaces may be used for magnetic recording.

In the above embodiment, the seed layer 13 is made of magnesium oxide or titanium nitride. However, the seed layer 13 is larger than 1 / n (n is a natural number) of the lattice constant of cobalt ferrite, and is equal to the 001 crystal plane of the cobalt ferrite. Other materials may be used as long as the lattice mismatch is a cubic crystal having a lattice constant within a predetermined range and the 001 crystal plane is oriented on the surface of the seed layer 13. Here, if the lattice constant of the material of the seed layer 13 is larger than 1 / n of the lattice constant of cobalt ferrite, tensile stress acts in the film surface at the interface, and perpendicular magnetic anisotropy is caused by the magnetoelastic effect of cobalt ferrite. Sex appears. Accordingly, it is necessary that the lattice constant of the material of the seed layer 13 is larger than 1 / n of the lattice constant of the cobalt ferrite under the condition that the cobalt ferrite grows epitaxially while reflecting the lattice constant of the seed layer 13. These conditions determine the range of allowable lattice constants. For example, when the perpendicular magnetic anisotropy of 1 × 10 ⁷ erg / cm ³ or more is required, the lattice constant of the material of the seed layer 13 is such that the degree of lattice mismatch with respect to 1 / n of the lattice constant of cobalt ferrite. It is set to be within the range of f = (− 1 ± 0.5)%.

  In addition, although the sputtering method used for generating the perpendicular magnetic recording layer 14 is high-frequency magnetron sputtering, it may be DC (Direct Current) pulse sputtering. At this time, a DC power source is used as a sputtering power source, and a switch that periodically switches ON / OFF is provided on the circuit.

  In the third embodiment, the soft magnetic backing layer 41 is composed of the first soft magnetic layer 411 made of an oxide, the nonmagnetic layer 412 made of an insulator, and the second soft magnetic layer 413 made of a metal. Although the seed layer 13 and the perpendicular magnetic recording layer 14 are formed on the substrate, the configuration of the soft magnetic backing layer 41 is not limited to this. As long as the seed layer 13 can be formed so that the 001 crystal plane is oriented on the surface of the seed layer 13, the soft magnetic backing layer 41 made of another material may be used.

  In the third embodiment, the seed layer 13 formed on the soft magnetic backing layer 41 is composed of magnesium oxide. However, as in the second embodiment, the seed layer 13 is composed of the first layer 131 made of magnesium oxide and the first layer 131. You may make it comprise the 2nd layer 132 which consists of titanium nitride.

DESCRIPTION OF SYMBOLS 1 ... Magnetic storage device 10, 30, 40 ... Perpendicular magnetic recording medium 101 ... Surface of perpendicular magnetic recording medium 11 ... Substrate 12 ... Soft magnetic layer 13 ... Seed layer 131 ... First layer 132 ... Second layer 14 ... Perpendicular magnetic recording Layer 20 ... Sputtering device 21 ... Chamber 22 ... Sample stand 23 ... Magnet 24 ... High frequency power supply 25 ... Oxygen gas generator 26 ... Variable leak valve 27 ... Nozzle 28 ... Target metal 41 ... Soft magnetic backing layer 411 ... First soft magnetic layer 412: Non-magnetic layer 413: Second soft magnetic layer 50: Recording / reproducing head 51 ... Write head 511 ... Main pole 512 ... Return pole 52 ... Read head 73 ... Housing 75 ... Hub 78 ... Suspension 79 ... Arm

Claims (16)

001 crystal plane of a seed layer made of a cubic crystal having a lattice constant larger than 1 / n (n is a natural number) of cobalt ferrite and having a lattice mismatch within a predetermined range with respect to the 001 crystal plane of the cobalt ferrite. In contrast, by performing reactive sputtering using oxygen as a reactive gas and iron cobalt alloy as a target metal, and having a perpendicular magnetic recording layer formed by growing a single crystal film or a highly oriented film of cobalt ferrite,
A perpendicular magnetic recording medium. The seed layer includes magnesium oxide or titanium nitride.
The perpendicular magnetic recording medium according to claim 1. The reactive sputtering is radio frequency magnetron sputtering or DC pulse magnetron sputtering.
The perpendicular magnetic recording medium according to claim 1, wherein the perpendicular magnetic recording medium is a magnetic recording medium. The reactive sputtering is planar sputtering in which an iron-cobalt alloy is disposed at a position facing the 001 crystal plane of the seed layer.
The perpendicular magnetic recording medium according to claim 1, wherein the perpendicular magnetic recording medium is a magnetic recording medium. The temperature of the production place of the perpendicular magnetic recording medium during the reactive sputtering is 600 ° C. or higher.
The perpendicular magnetic recording medium according to claim 1, wherein the perpendicular magnetic recording medium is a magnetic recording medium. A first soft magnetic layer made of an oxide having a spinel-type or inverse spinel-type ionic crystal structure; and a second soft magnetic layer made of a single metal having ferromagnetism or an alloy containing a single metal having ferromagnetism; A soft magnetic backing layer comprising
The seed layer is laminated on a surface of the second soft magnetic layer opposite to the first soft magnetic layer;
The perpendicular magnetic recording medium according to claim 1, wherein the perpendicular magnetic recording medium is a magnetic recording medium. The oxide is an oxide containing triiron tetroxide or maghemite, the metal is iron, and the alloy containing the metal is an alloy containing iron,
The soft magnetic backing layer further includes a nonmagnetic layer made of an insulator between the first soft magnetic layer and the second soft magnetic layer.
The perpendicular magnetic recording medium according to claim 6.   A magnetic storage device comprising: the perpendicular magnetic recording medium according to claim 1; and a head that records or reproduces information on the perpendicular magnetic recording medium. A method of manufacturing a perpendicular magnetic recording medium having a perpendicular magnetic recording layer made of cobalt ferrite,
001 crystal of a seed layer made of a cubic crystal having a lattice constant larger than 1 / n (n is a natural number) of the cobalt ferrite and having a lattice mismatch with respect to the 001 crystal plane of the cobalt ferrite within a predetermined range. Reactive sputtering using oxygen as a reactive gas and an iron cobalt alloy as a target metal is performed on the surface to grow the single crystal film or highly oriented film of cobalt ferrite, thereby forming the perpendicular magnetic recording layer Having steps,
A method of manufacturing a perpendicular magnetic recording medium. The seed layer includes magnesium oxide;
A step of generating a seed layer by forming a magnesium oxide thin film so that a 001 crystal plane of the magnesium oxide is oriented on the surface of the seed layer;
The method of manufacturing a perpendicular magnetic recording medium according to claim 9. The seed layer includes magnesium oxide and titanium nitride,
After forming a magnesium oxide thin film so that the 001 crystal plane of the magnesium oxide is oriented on the surface, the titanium nitride is deposited on the 001 crystal plane of the magnesium oxide, thereby forming the titanium nitride on the surface of the seed layer. A step of generating a seed layer so that the 001 crystal plane is oriented.
The method of manufacturing a perpendicular magnetic recording medium according to claim 9. The reactive sputtering is RF magnetron sputtering or DC pulse magnetron sputtering.
12. The method of manufacturing a perpendicular magnetic recording medium according to claim 9, wherein The reactive sputtering is planar sputtering in which an iron-cobalt alloy is disposed at a position facing the 001 crystal plane of the seed layer.
The method for manufacturing a perpendicular magnetic recording medium according to claim 9, wherein: The temperature of the production place of the perpendicular magnetic recording medium during the reactive sputtering is 600 ° C. or higher.
14. The method of manufacturing a magnetic material for a perpendicular magnetic recording medium according to claim 9, wherein the magnetic material is a magnetic material. Producing a first soft magnetic layer made of an oxide having a spinel-type or inverse spinel-type ionic crystal structure;
Forming a nonmagnetic layer made of an insulator on the first soft magnetic layer;
Producing a second soft magnetic layer made of a metal having ferromagnetic property alone or an alloy containing a metal having ferromagnetic property alone on the non-magnetic layer, and
Generating the seed layer on the second soft magnetic layer;
15. The method of manufacturing a perpendicular magnetic recording medium according to claim 9, wherein The oxide is an oxide containing triiron tetroxide or maghemite, the insulator is magnesium oxide, the metal is iron, and the alloy containing the metal is an alloy containing iron.
The method of manufacturing a perpendicular magnetic recording medium according to claim 15.

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