A high magnetic performance magnetic code disk FeCoCr material and its preparation method

Abstract

The present invention provides a high magnetic performance magnetic code disk FeCoCr material and a preparation method thereof, relating to the technical field of magnetic materials, including: (1) by means of magnetron sputtering, on a substrate, sequentially and alternately direct current sputtering a B target, an FeCoCr target, a B target and an FeCoCr target, and then sputtering a Ta layer to obtain a as-prepared film; (2) performing a stepped annealing treatment on the as-prepared film. The present invention improves the hard magnetism of the FeCoCr alloy film while achieving a more uniform microstructure, provides important scientific data support for its application in the field of high-density magnetic code disks, and has a lower cost.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic materials, and in particular to a high-magnetic-performance magnetic code disk FeCoCr material and a preparation method thereof, which can achieve a synergistic improvement in the coercive force and remanence of a semi-hard magnetic alloy film. Background Art

[0002] A magnetic encoder is a non-contact position sensor that uses the magnetoresistive effect to convert key motion information, such as the rotation angle and speed of the detected object, into a digital electrical signal. It is widely used in high-precision control applications such as high-end CNC machine tools. The accuracy of a magnetic encoder directly impacts the machining accuracy of CNC machines, and its accuracy depends on the density and uniformity of the magnetic pole signal. Compared to optical encoders, magnetic encoders offer a variety of advantages, including vibration resistance, corrosion and contamination resistance, low cost, and a simple structure, leading to their increasing application.

[0003] The core of magnetic encoding devices is a magnetic code disk material with excellent magnetic properties. Based on the actual application requirements of the magnetic code disk, the code disk material must possess both moderate coercivity and high remanence to facilitate the writing (magnetization) and detection of magnetic pole signals. Sufficient remanence ensures reliable output signal strength, while relatively high coercivity ensures sufficient resistance to electromagnetic interference while facilitating the writing of magnetic poles.

[0004] FeCoCr-based alloy films with amplitude modulation decomposition characteristics are an important component of the permanent magnet material family. Compared to numerous alloy materials such as SmCo, NdFeB, Fe(Co)Pt, and CoCrTa, semi-hard FeCoCr-based alloy films offer practical advantages such as excellent mechanical properties, the absence of rare earth or precious metal elements, a high Curie temperature (Tc approximately 650°C), and ease of magnetization. They are expected to be used as a new magnetic encoding recording material in future high-precision magnetic encoders. Furthermore, considering the practical application requirements of magnetic code disk materials, the uniformity of the magnetic code disk material has a significant impact on the accuracy of the magnetic encoder and the stability of the recorded magnetic signal. To ensure the anti-disturbance and read / write performance requirements of the magnetic pole signal recorded by the magnetic code disk, it is also necessary to address the uniformity and consistency of the microstructure.

[0005] Therefore, improving the magnetic properties and regulating the uniformity of FeCoCr magnetic code disk materials are of great significance to the development of high-precision magnetic encoders. How to improve the magnetic properties of FeCoCr thin film materials while maintaining the uniformity of the material at small scales is a key issue that needs to be solved urgently. Summary of the Invention

[0006] In view of the problem that it is difficult to simultaneously improve the coercivity and remanence of the magnetic disk thin film material FeCoCr, and at the same time ensure the uniformity of the magnetic disk material, the present invention proposes a method to simultaneously greatly improve the coercivity and remanence of the FeCoCr thin film through material structure design and ensure the uniformity of the material. Specifically, the technical solution of the present invention is as follows:

[0007] A preparation method of a high-magnetic-performance magnetic disk FeCoCr material, comprising the following steps:

[0008] (1) By magnetron sputtering method, on the substrate, the B target, FeCoCr target, B target and FeCoCr target are alternately sputtered by DC in sequence, and then the Ta layer is sputtered to obtain a as-prepared film; by constructing a two-period multilayer film structure of [B / FeCoCrMoTi]2, it is more conducive to realizing the complete spinodal decomposition of the FeCoCr-based thin film, and simultaneously greatly improving the coercivity and remanence. Specifically, after high-temperature annealing, B atoms preferentially combine with Cr atoms to form the CrB2 phase, reducing the concentration of Cr atoms in the FeCo-rich phase, and even generating the FeCo ferromagnetic phase in some regions, which can greatly improve the remanent magnetization intensity. The two-period structure can make B combine with Cr more fully.

[0009] Preferably, the FeCoCr target used in sputtering is an FeCoCrMoTi alloy target, and the nominal composition of the target is Fe:Co:Cr:Mo:Ti = 42:25:30:3:1 (wt%), and FeCoCrMoTi can be abbreviated as FeCoCr.

[0010] During sputtering, the base vacuum is lower than 3×10 -5 Pa, and the Ar gas partial pressure is maintained at 0.4 Pa.

[0011] (2) Perform stepwise annealing treatment on the as-prepared film.

[0012] Preferably, the vacuum degree of the stepwise annealing treatment is ≤5×10 -5 Pa. First, anneal at a constant temperature of 700 - 750 °C for 15 - 25 min, and then reduce the temperature to 600 - 650 °C and anneal at a constant temperature for 25 - 35 min. By stepwise annealing at two temperatures, it is beneficial to obtain high magnetic properties.

[0013] Preferably, the stepwise annealing is first annealed at a constant temperature of 700 °C for 20 min, and then the temperature is reduced to 630 °C and annealed at a constant temperature for 30 min.

[0014] Preferably, the substrate material is selected from a silicon substrate or a non-magnetic stainless steel substrate.

[0015] Preferably, the reaction conditions for sputtering the B target are a sputtering power of 200 W and a sputtering time of 11 minutes and 6 seconds; the conditions for sputtering the FeCoCr target are a sputtering power of 100 W and a sputtering time of 27 minutes and 30 seconds; the conditions for sputtering the Ta layer are a sputtering power of 50 W and a sputtering time of 5 minutes and 33 seconds.

[0016] The present invention also provides a high magnetic performance magnetic code disk FeCoCr material prepared by the above method, including a substrate, a B layer, a FeCoCrMoTi layer, and a protective layer, wherein the thickness of the B layer is 10 - 50 nm, and the thickness of the FeCoCrMoTi layer is 100 nm.

[0017] Preferably, the thickness of the B layer is 20 nm, and the thickness of the FeCoCrMoTi layer is 100 nm.

[0018] Preferably, the structure of the FeCoCr material is: substrate / B / FeCoCrMoTi / B / FeCoCrMoTi / Ta.

[0019] Furthermore, the material of the present invention is applied to the field of magnetic code disks of high-precision magnetic encoders.

[0020] The beneficial effects brought by the technical solution of the present invention at least include:

[0021] After introducing a 20 nm B layer into the FeCoCr thin film, the coercivity and remanence of the present invention reach 610 Oe and 5340 Oe respectively, which are increased by 24.5% and 135.1% compared with the FeCoCrMoTi single-layer film, and can meet the actual application requirements of the magnetic encoder code disk. At the same time, the atomic radius of B is small, and its diffusion behavior during the annealing process has little influence on the uniformity of the thin film microstructure.

[0022] According to thermodynamics and the enthalpy change difference of the chemical reaction between B atoms and the three solvent atoms Fe, Co, and Cr, B atoms preferentially combine with Cr atoms to form the CrB2 phase, while repelling Co or Fe atoms, which is beneficial to further reducing the Cr content in the FeCo-rich phase. The concentration difference of Cr atoms between the Fe-Co-rich phase and the Cr-rich phase will gradually increase, thus promoting the further progress of spinodal decomposition. And the experimental results show that the newly formed CrB2 phase and Fe 0.7 Co 0.3 phase unit cell volumes in the wave thin film are 23.45 Å 3 and 23.52 Å 3 respectively, which are very close to the spinodal decomposition phase, and are beneficial to improving the uniformity of the nano-scale microstructure. Therefore, the present invention realizes a more uniform microstructure while improving the hard magnetism of the FeCoCr alloy thin film, provides important scientific data support for its application in the field of high-density magnetic code disks, and has a lower cost. Description of the Drawings

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0024] Figure 1 M-H curves of FeCoCrMoTi thin films without B intercalation and after introducing B intercalation, where (a) is the FeCoCrMoTi (200 nm) single-layer film sample; (b) is the multi-layer film sample of B (20 nm) / FeCoCrMoTi (100 nm) / B (20 nm) / FeCoCrMoTi (100 nm).

[0025] Figure 2 (a) and (b) are the high-resolution XPS spectra of B 1s obtained from the single-layer film sample and the multi-layer film sample before and after introducing the B layer at different etching depths, respectively. Detailed implementation manners

[0026] The following will describe the technical solutions in the present invention with reference to the accompanying drawings.

[0027] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as an "example" in the present invention should not be construed as being more preferred or more advantageous than other embodiments or design solutions. Exactly, the use of the word "example" is intended to present concepts in a specific manner. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one of the two.

[0028] In the embodiments of the present invention, "image" and "picture" can sometimes be used interchangeably. It should be noted that when the difference is not emphasized, the meanings they express are the same. "Of", "corresponding" and "correspondent" can sometimes be used interchangeably. It should be noted that when the difference is not emphasized, the meanings they express are the same.

[0029] In the embodiments of the present invention, sometimes subscripts such as W1 may be miswritten as non-subscript forms such as W1. When the difference is not emphasized, the meanings they express are the same.

[0030] To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

[0031] Embodiment 1

[0032] Step S1: Provide a base layer and an FeCoCrMoTi alloy target. The nominal composition of the target is Fe:Co:Cr:Mo:Ti = 42:25:30:3:1 (wt%); the base layer is a silicon substrate.

[0033] Step S2: By means of magnetron sputtering, on the substrate, alternately sputter the B target, the FeCoCr target, the B target and the FeCoCr target in sequence, and then sputter the Ta layer to obtain a as-prepared film; during the sputtering process, the background vacuum is lower than 3×10 -5 Pa, and the Ar gas partial pressure is maintained at 0.4 Pa; the reaction conditions for sputtering the B target are a sputtering power of 200 W, a sputtering rate of 0.03 nm / s, and a sputtering time of 11 minutes and 6 seconds; the conditions for sputtering the FeCoCr target are a sputtering power of 100 W, a sputtering rate of 0.06 nm / s, and a sputtering time of 27 minutes and 30 seconds; the conditions for sputtering the Ta layer are a sputtering power of 50 W, a sputtering rate of 0.03 nm / s, and a sputtering time of 5 minutes and 33 seconds.

[0034] Step S3: Anneal the as-prepared film at a constant temperature of 700°C for 20 min, and then reduce the temperature to 630°C and anneal at a constant temperature for 30 min. The vacuum degree of the annealing environment is better than 5×10 -5 Pa.

[0035] The structure of the magnetic code disk thin film material FeCoCr prepared in this embodiment is: substrate / B(20nm) / FeCoCrMoTi(100nm) / B(20nm) / FeCoCrMoTi(100nm) / Ta.

[0036] Comparative Example 1

[0037] The difference from Example 1 is that in step S2, the FeCoCr target is only sputtered on the substrate once. The structure of the magnetic code disk thin film material FeCoCr prepared is: substrate / FeCoCrMoTi(100nm) / Ta(10nm).

[0038] Comparative Example 2

[0039] The difference from Example 1 is that in step S2, the B target and the FeCoCr target are only sputtered on the substrate once. The structure of the magnetic code disk thin film material FeCoCr prepared is: substrate / B(20nm) / FeCoCrMoTi(100nm) / Ta(10nm).

[0040] The coercivity is about 400 Oe, and the remanent magnetization is 3000 Oe.

[0041] As Figure 1(a) and (b) are the M-H curves of the FeCoCrMoTi thin film before and after introducing the B layer, respectively. As can be seen from the figure, the coercivity and remanence of the thin film are significantly improved after introducing the B layer. Specifically, before introducing the B layer, the in-plane coercivity of the FeCoCrMoTi single-layer film sample is 490 Oe, and the remanent magnetization is 185 emu / cm 3 (2325 Oe). When the B interlayer thickness is 20 nm, the in-plane coercivity, remanent magnetization, and saturation magnetization all increase rapidly with the increase of the B layer thickness. When the B interlayer thickness is 20 nm, the coercivity reaches the maximum value of 610 Oe, and the remanent magnetization is 435 emu / cm 3 (5466 Oe). Compared with the FeCoCrMoTi single-layer film, the coercivity and remanence are increased by 24.5% and 135.1% respectively. At the same time, the material has the uniformity of the nano-scale microstructure.

[0042] Figure 2 High-resolution XPS spectra of B1s obtained from the FeCoCrMoTi single-layer film sample and the multi-layer film sample before and after introducing the B layer at different etching depths are shown in (a) and (b), respectively. This indicates the presence of the CrB2 phase in the multi-layer film sample of [B(20 nm) / FeCoCrMoTi(100 nm)]2.

[0043] In the single-layer film sample, with the progress of the spinodal decomposition process, the concentration difference of Cr atoms between the Fe-Co-rich phase and the Cr-rich phase gradually increases, and the gradient energy and strain energy also increase accordingly. When the concentration difference between the two phases reaches a certain value, the gradient energy and strain energy will hinder the further progress of the spinodal decomposition. However, for the multi-layer film sample after introducing the B interlayer, B atoms tend to combine with Cr atoms to form the CrB2 phase and repel Fe or Co atoms. This chemical energy overcomes the gradient energy and strain energy, expands the composition difference between the FeCo-rich phase and the Cr-rich phase, and leads to the formation of a new Fe 0.7 Co 0.3 magnetic-enhanced phase, thus effectively promoting the spinodal decomposition reaction. As a result, the remanent magnetization is greatly improved. The generation of the secondary phase (Fe 0.7 Co 0.3 phase and CrB2 phase) and the enhanced pinning of domain walls caused by the increased phase composition difference are the main reasons for the increase in coercivity. The present invention effectively promotes the spinodal decomposition reaction by introducing chemical energy through doping with B elements to overcome the gradient energy and strain energy, opening up a new feasible way for the synchronous optimization of the coercivity and remanence properties of the FeCoCr semi-hard magnetic alloy. In addition, by taking advantage of the small atomic radius of B atoms, the influence on the uniformity of the thin film microstructure is minimized as much as possible, which is beneficial to improving the uniformity of the nano-scale microstructure. The present invention enables the improvement of the magnetic properties of the thin film while taking into account the uniformity of the material, providing an important scientific basis for the preparation and application of new high-performance magnetic disk.

[0044] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the said claims.

Claims

1. A preparation method of a high magnetic performance magnetic code disk FeCoCr material, characterized in that, It includes the following steps: (1) By means of magnetron sputtering method, on a substrate, B target, FeCoCrMoTi alloy target, B target and FeCoCrMoTi alloy target are alternately sputtered by DC in sequence, and then Ta layer is sputtered to obtain as-prepared film; The background vacuum degree during the sputtering process is lower than 3×10 -5 Pa, and the partial pressure of Ar gas is maintained at 0.4 Pa; (2) The as-prepared film is subjected to stepwise annealing treatment; The structure of FeCoCr material is: substrate / B / FeCoCrMoTi / B / FeCoCrMoTi / Ta; The nominal composition of the FeCoCrMoTi alloy target used in sputtering is Fe:Co:Cr:Mo:Ti = 42:25:30:3:

1.

2. The method according to claim 1, characterized in that, The vacuum degree of the step annealing treatment ≤ 5×10 -5 Pa. First, perform isothermal annealing at 700 - 750°C for 15 - 25 min, and then reduce the temperature to 600 - 650°C for isothermal annealing for 25 - 35 min.

3. The method according to claim 2, wherein The stepwise annealing is first carried out at a constant temperature of 700 °C for 20 min, and then the temperature is reduced to 630 °C for constant temperature annealing for 30 min.

4. The method according to claim 1, wherein The substrate material is selected from a silicon substrate or a non-magnetic stainless steel substrate.

5. The method according to claim 1, characterized in that, The reaction conditions for sputtering the B target are a sputtering power of 200 W and a sputtering time of 11 minutes and 6 seconds; the conditions for sputtering the FeCoCrMoTi alloy target are a sputtering power of 100 W and a sputtering time of 27 minutes and 30 seconds; the conditions for sputtering the Ta layer are a sputtering power of 50 W and a sputtering time of 5 minutes and 33 seconds.

6. The high magnetic performance magnetic code disk FeCoCr material prepared by the method according to any one of claims 1-5, characterized in that, It includes a substrate, a B layer, a FeCoCrMoTi layer and a Ta layer, wherein the thickness of the B layer is 10-50 nm and the thickness of the FeCoCrMoTi layer is 100 nm.

7. The FeCoCr material according to claim 6, characterized in that, The thickness of the B layer is 20 nm and the thickness of the FeCoCrMoTi layer is 100 nm.

8. Application of the FeCoCr material prepared by the method according to any one of claims 1-5 or the FeCoCr material according to any one of claims 6-7 in the field of magnetic code disks of high-precision magnetic encoders.

Images