Rare earth element doped AlNiCo magnetic film material and preparation method thereof

Abstract

The invention discloses a high-performance rare earth doped AlNiCo thin film material as well as a preparation method and application thereof. A multi-target co-sputtering method is adopted, a high-vacuum magnetic control multi-target co-sputtering system is utilized, a rare earth element doped AlNiCo thin film is deposited on a silicon substrate, the silicon substrate, a metal AlNiCo target and a rare earth metal target are placed in a sputtering cavity, the background vacuum degree in the AlNiCo thin film deposition process is larger than or equal to 5 * 10 <-4 > Pa, and the argon atmosphere is adopted during deposition. And high-vacuum in-situ heat treatment is conducted on the prepared film sample, after annealing is completed, the sample is taken out after the temperature in the cavity is reduced to 100 DEG C or below, and the AlNiCo film evenly doped with the rare earth elements is obtained. The high-performance rare earth doped AlNiCo thin film material has the advantages of large coercive force, good temperature stability and the like, the preparation method is simple, the production cost is low, and the high-performance rare earth doped AlNiCo thin film material is suitable for large-scale industrial production and application.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic thin film materials, and in particular to a rare earth element-doped AlNiCo magnetic thin film material prepared by magnetron multi-target co-sputtering, a preparation method thereof, and applications thereof. Background Art

[0002] Aluminum-nickel-cobalt (AlNiCo) is a first-generation permanent magnet material, primarily composed of aluminum, nickel, cobalt, iron, and other trace metal elements. AlNiCo magnets offer advantages such as high remanence, high Curie temperature, and excellent temperature stability. They are currently the most temperature-stable permanent magnet alloy and are suitable for high-temperature applications such as quartz flexible accelerometers and aerospace electromagnetic relays. However, the current trend toward highly integrated and miniaturized electronic components presents a significant challenge with heat accumulation. As the temperature of a typical magnet increases, its magnetic field becomes unstable or even completely demagnetized. Therefore, AlNiCo is an ideal magnetic material for the production of such miniature mechanical components.

[0003] A disadvantage of AlNiCo permanent magnets is their very low coercivity. Unlike rare earth permanent magnets with high magnetocrystalline anisotropy, their coercivity stems primarily from shape anisotropy, which is caused by the oriented arrangement of iron-cobalt-rich nanorods. A larger aspect ratio of the nanorods increases the shape anisotropy, remanence, and coercivity. However, thin-film AlNiCo materials, limited by the size of the nanocrystals and the presence of amorphous regions, cannot form a large-scale, parallel-oriented nano-spindle structure. Consequently, the coercivity and remanence of AlNiCo films are inferior to those of bulk AlNiCo. Therefore, the key to developing AlNiCo magnetic thin-film materials is to improve their coercivity while ensuring high temperature stability. To achieve this goal in bulk AlNiCo, researchers typically add heavy rare earth elements to compensate for the material's temperature stability. However, this addition reduces the magnet's saturation magnetization, which in turn reduces its maximum energy product. Furthermore, the limited reserves and high cost of heavy rare earth elements increase the production cost of magnets. Considering that the exchange interaction between the 4f electrons of light rare earth elements and the 3d electrons of transition metals is usually ferromagnetic, this interaction leads to the compounds having high magnetization and T c This is beneficial for high performance permanent magnet materials. Among them, SmCo5 and Sm2Co in Sm-Co based alloys 17 The magnetocrystalline anisotropy constant is large and the temperature stability is high. SmCo5 is a hexagonal crystal system with an ultra-high magnetocrystalline anisotropy constant K1=2×10 6 J / m3, the theoretical anisotropy field is up to 400kOe; Sm2Co 17 Magnet, this compound has a uniaxially symmetrical hexagonal crystal structure, a Curie temperature of 917°C, and a magnetocrystalline anisotropy field of 60kOe.

[0004] Therefore, in this study, metal Sm was selected as the doping element of the film. Evenly doping the Sm element into the AlNiCo film in a certain proportion may solve the above problems to a certain extent. However, there is no relevant report on the research of RE-AlNiCo composite films. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desired to provide a rare earth element-doped AlNiCo thin film material and a preparation method thereof.

[0006] The present invention provides a preparation method and application of a rare earth element-doped AlNiCo thin film material, comprising the following steps:

[0007] 1) Cleaning high-purity single crystal silicon substrate

[0008] Immerse the silicon substrate in anhydrous ethanol for ultrasonic cleaning, and blow dry the cleaned silicon substrate with hot air for later use;

[0009] 2) Preparation of doped metal films

[0010] A multi-target co-sputtering method is used to deposit a rare earth element-doped AlNiCo thin film on a silicon substrate using a high vacuum magnetron multi-target co-sputtering system: the silicon substrate, the metal AlNiCo target, and the rare earth element target dried in step 1) are placed in a sputtering chamber, and the sputtering chamber is evacuated. When the vacuum degree reaches the required level, argon gas is introduced and the chamber pressure is adjusted. The sputtering power, sputtering time, and target-substrate distance parameters are set to obtain a doped metal thin film sample;

[0011] 3) In-situ annealing of doped metal films

[0012] Performing a high vacuum in-situ heat treatment on the thin film sample prepared in step 2, evacuating the chamber, and then setting the annealing temperature and heat treatment time parameters for the heat treatment;

[0013] 4) Obtaining rare earth element doped AlNiCo film

[0014] After the annealing is completed, the sample is taken out after the temperature in the chamber drops below 100° C. to obtain a rare earth element-doped AlNiCo film.

[0015] Preferably, the silicon substrate in step 1) is a single-sided polished high-purity single-crystalline silicon substrate with a 200nm oxide layer, a size of 0.7cm×0.7cm, a thickness of 250-500μm, a flatness of <3μm, and a roughness of <0.5nm; the silicon substrate is cleaned by ultrasonic cleaning in deionized water and ≥99.5wt% anhydrous ethanol for 60min respectively, and then dried with hot air before use immediately.

[0016] Preferably, in step 2), the cleaned silicon substrate is placed on the sample stage of the sputtering chamber and on the cathode target base; the sputtering chamber is evacuated to 5×10 -4 Pa, the base distances between the AlNiCo target and the Sm target are 5-9 cm and 5-11 cm respectively, the sputtering power of the AlNiCo target is 30w-180w, the argon flow rate is set to 24sccm-45sccm and the working pressure is maintained at 0.1Pa-1.8Pa; pre-sputtering is carried out first to remove impurities and possible oxide layers on the surface of the target, and then formal sputtering is carried out at room temperature for 15-60min.

[0017] Preferably, the purity of the metal target material is higher than 99.9%.

[0018] Preferably, the AlNiCo target material is one of the AlNiCo materials with grades 1 to 9.

[0019] Preferably, the doping element of the AlNiCo film includes at least one of Sm, Ce, Y, Dy, Nd, Pr, Gd, Sc, La, Pm, and Tb.

[0020] Preferably, the AlNiCo film has a thickness of 50 nm to 1000 nm.

[0021] Preferably, the surface of the AlNiCo film is also covered with a protective layer.

[0022] Preferably, the protective layer is composed of at least one of Cr, Ti, Ta, and Ru.

[0023] Preferably, the AlNiCo thin film is prepared by one of magnetron sputtering, multi-arc ion plating, pulsed laser deposition, electron beam evaporation, and atomic deposition.

[0024] Preferably, the background vacuum degree during the AlNiCo film deposition process is ≥5×10 -4 Pa, Ar atmosphere is used during deposition, the deposition pressure is 0.1Pa~100Pa, the AlNiCo sputtering deposition power is 30W~180W, and the rare earth element deposition power is 10~80W.

[0025] Preferably, the protective layer is prepared by one of magnetron sputtering, multi-arc ion plating, pulsed laser deposition, electron beam evaporation, and atomic deposition.

[0026] Preferably, the background vacuum degree during the deposition of the protective layer is ≥5×10 -4 Pa, Ar atmosphere is used during deposition, the deposition pressure is 0.1Pa~100Pa, and the sputtering deposition power is 60W~200W.

[0027] Preferably, the annealing treatment is performed at a temperature of 500° C. to 700° C., and the holding time is 0.5 h to 5 h.

[0028] Preferably, the annealing treatment is a high vacuum in-situ heat treatment, and the background vacuum is lower than 5×10 -4 Pa.

[0029] On the other hand, the present application provides a rare earth element doped AlNiCo magnetic thin film material, comprising: a silicon substrate, a silicon oxide layer, an AlNiCo thin film deposited on the substrate, and a metal film protective layer; wherein the AlNiCo thin film is doped with at least one of lanthanide elements, Sc or Y among the rare earth elements to form a rare earth doped AlNiCo magnetic thin film layer.

[0030] In some embodiments, a silicon oxide layer is located on the silicon substrate.

[0031] In some embodiments, the atomic percentage of the rare earth element is between 0.3% and 25%.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) The method for preparing rare earth element-doped AlNiCo thin film materials of the present invention, wherein the coercivity, maximum magnetic energy product and temperature stability of the Sm-doped AlNiCo thin film prepared by the process method are significantly improved compared with AlNiCo magnetic thin films;

[0034] 2) The rare earth element-doped AlNiCo thin film material of the present invention has the advantages of high coercivity, high remanence, high magnetic energy product, and good temperature stability, and is suitable for use in microelectronic devices (e.g., micro inertial navigation devices, micro magnetic encoders, etc.), and has broad application prospects;

[0035] 3) The present invention provides a method for preparing a rare earth element-doped AlNiCo thin film material. The multi-target magnetron sputtering process adopted in the invention is simple, reliable, highly repeatable, and the grown film is uniform and dense, which is suitable for large-scale industrial production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The model used in this series is the IBVTC450 ion beam assisted three-target magnetron sputtering instrument.

[0037] Figure 2 Schematic diagram of target positions for multi-target co-sputtering.

[0038] Figure 3 1 and 2 are demagnetization curves of the AlNiCo magnetic thin film materials in Example 1, Example 2, Example 3 and Comparative Example 1 at different temperatures.

[0039] Figure 4 1 is the remanence change curve of the AlNiCo magnetic thin film material in Example 1, Example 2, Example 3 and Comparative Example 1 at 200K~400K.

[0040] Figure 5 1 is a coercive force variation curve of the AlNiCo magnetic thin film material in Example 1, Example 2, Example 3 and Comparative Example 1 at 200K~400K.

[0041] Figure 6 1 is a curve showing the change in saturation magnetization intensity of the AlNiCo magnetic thin film materials in Example 1, Example 2, Example 3 and Comparative Example 1 at 200K to 400K.

[0042] Figure 7 1 is the XRD diagram of the AlNiCo magnetic thin film materials in Example 1, Example 2, Example 3 and Comparative Example 1.

[0043] Figure 8 This is the EDS result of the thin film. DETAILED DESCRIPTION

[0044] The present invention will be further explained and illustrated below with reference to specific embodiments.

[0045] Example 1:

[0046] A high-performance rare earth-doped AlNiCo thin film material, the preparation method of which is as follows:

[0047] The silicon substrate is a single-sided polished, high-purity single-crystal silicon substrate with a 200nm oxide layer, measuring 0.7cm×0.7cm, 250-500μm thick, with a flatness of <3μm and a roughness of <0.5nm. The silicon substrate is cleaned by ultrasonic cleaning in deionized water and ≥99.5wt% anhydrous ethanol for 60 minutes, then blown dry with hot air before immediate use. A multi-target co-sputtering method is used to deposit an Sm-doped AlNiCo thin film on the silicon substrate using a high-vacuum magnetron multi-target co-sputtering system. The dried silicon substrate, metal AlNiCo target, and metal Sm target are placed in a sputtering chamber, which is then evacuated. The background vacuum during the AlNiCo film deposition process is ≥5×10 -4Pa, an argon atmosphere with a deposition pressure of 0.8 Pa was used for deposition. Once the required vacuum level was achieved, argon was introduced and the chamber pressure was adjusted. The sputtering power for AlNiCo was set to 80W DC and for Sm to 10W RF, resulting in metal film samples. The targets used were an AlNiCo 5 alloy target (processed from a commercial AlNiCo 5 alloy; the mass fraction of the components is: Fe: 49%; Co: 25%; Ni: 15%; Al: 7%; Cu: 4%) and a pure Sm target. The substrate distances between the AlNiCo target and the rare earth metal target were 5-9cm and 5-11cm, respectively. The argon flow rate was set at 24sccm to 45sccm. A pre-sputtering process was performed to remove impurities and any oxide layer from the target surface, followed by co-sputtering at room temperature for 15 minutes. A protective layer was then sputtered using a metallic Cr target. The sputtering power source was an RF power supply, the sputtering power was 80W, the sputtering time was 8 minutes, and the deposition pressure was 0.4 Pa. The sputtering deposition was performed on a rotating sample stage. The prepared film sample was then subjected to a high-vacuum in-situ heat treatment. The chamber was evacuated and the annealing temperature was set to 600°C for 1 hour. After the annealing was complete, the sample was removed from the chamber after the temperature dropped below 100°C, resulting in a 200nm thick AlNiCo film with a Sm content of 3.099%.

[0048] Example 2:

[0049] A high-performance rare earth-doped AlNiCo thin film material is prepared in the same manner as in Example 1, except that the radio frequency power is adjusted from 10W to 15W during preparation.

[0050] Example 3:

[0051] A high-performance rare earth-doped AlNiCo thin film material is prepared in the same manner as in Example 1, except that the radio frequency power is adjusted from 15W to 20W during preparation.

[0052] Comparative Example 1:

[0053] An AlNiCo magnetic thin film material is prepared in the same manner as in Example 1 except that the sputtering power of the Sm target is adjusted to 0.

[0054] Characterization of ingredients:

[0055] The EDS images of Example 1, Example 2 and Example 3 are as follows: Figure 8 The atomic percentages of specific elements are shown in the following table.

[0056] Aluminum Iron Cobalt Nickel Copper Samarium Example 1 26.979 27.650 23.273 15.787 3.213 3.099 Example 2 27.797 27.034 23.308 15.543 2.970 3.347 Example 3 30.141 26.387 22.249 14.655 2.311 4.256

[0057] Performance testing:

[0058] 1) Demagnetization curves of the AlNiCo magnetic thin film materials in Example 1, Example 2, Example 3 and Comparative Example 1 at different temperatures are as follows: Figure 3 As shown in the figure, the remanence change curve at 200K~400K is as follows Figure 4 As shown in the figure, the coercive force variation curve at 200K~400K is as follows Figure 5 As shown in the figure, the saturation magnetization intensity change curve at 200K~400K is as follows Figure 6 shown.

[0059] Note: The temperature stability of magnetic properties of magnets generally includes two aspects, namely, the temperature stability of remanence and the temperature stability of coercivity. The temperature stability of remanence is quantified by the temperature coefficient of remanence (α), and the temperature stability of coercivity is quantified by the temperature coefficient of coercivity (β). The expressions are respectively as formula (1) and formula (2):

[0060] Formula (1):

[0061] Formula (2):

[0062] In the above formula, M r (T0) and M r (T1) are the remanence values at T0 and T1 respectively, H r (T0) and H r (T1) are the coercive force values at temperatures T0 and T1, respectively.

[0063] The remanence change test data, coercivity change test data, saturation magnetization change test data and maximum magnetic energy product change test data of the AlNiCo magnetic film materials in Examples 1 to 3 and Comparative Example 1 in the temperature range of 200K to 400K are shown in the following table:

[0064] Table 1 Remanence change test data

[0065] Mr 200k(kGs) 300k(kGs) 400k(kGs) Temperature coefficient (% / K) Comparative Example 1 4.38 3.96 3.59 -0.09018 Example 1 2.62 2.46 2.31 -0.05916 Example 2 2.48 2.36 2.19 -0.05847 Example 3 1.98 1.81 1.67 -0.07828

[0066] Table 2 Coercivity change test data

[0067] Hc 200k(Oe) 300k(Oe) 400k(Oe) Temperature coefficient (% / K) Comparative Example 1 175.887 166.068 152.397 -0.06678 Example 1 266.041 252.112 234.242 -0.06164 Example 2 319.483 309.998 283.244 -0.05671 Example 3 338.524 323.622 286.918 -0.07622

[0068] Table 3 Saturation magnetization change test data

[0069] Ms 200k(kGs) 300k(kGs) 400k(kGs) Comparative Example 1 10.29 9.68 8.94 Example 1 8.21 6.03 5.53 Example 2 6.29 5.65 5.33 Example 3 5.45 5.09 4.92

[0070] Depend on Figures 3 to 6 It can be seen that:

[0071] a) The coercivity and temperature stability of the high-performance rare earth-doped AlNiCo thin film materials in Examples 1, 2, and 3 are significantly higher than those of the AlNiCo magnetic thin film material in Comparative Example 1. At room temperature, the coercivity of the AlNiCo magnetic thin film material in Comparative Example 1 is only 166.068 Oe, while the coercivity of the Sm-doped AlNiCo magnetic thin film material in Example 1 reaches 252.112 Oe, an increase of 51.8%. The coercivity of the Sm-doped AlNiCo magnetic thin film material in Example 2 reaches 309.998 Oe, an increase of 86.67%. The coercivity of the Sm-doped AlNiCo magnetic thin film material in Example 3 reaches 338.524 Oe, an increase of 103.85%.

[0072] b) The remanence temperature coefficient and coercivity temperature coefficient of the AlNiCo magnetic thin film material in Comparative Example 1 are -0.09018% / K and -0.06678% / K, respectively, while the remanence temperature coefficient and coercivity temperature coefficient of the Sm-doped AlNiCo magnetic thin film material in Example 1 are -0.05916% / K and -0.06164% / K, respectively, and the remanence temperature stability and coercivity temperature stability thereof are improved by 34.4% and 7.7%, respectively. The remanence temperature coefficient and coercivity temperature coefficient of the Sm-doped AlNiCo magnetic thin film material in Example 2 are -0.05847% / K and -0.05671% / K, respectively, and the remanence temperature stability and coercivity temperature stability thereof are improved by 35.16% and 15.08%, respectively. The remanence temperature coefficient of the Sm-doped AlNiCo magnetic thin film material in Example 3 is -0.07828% / K, and the remanence temperature stability thereof is improved by 13.2%. Obviously, the remanence temperature stability and coercivity temperature stability of the Sm-doped AlNiCo magnetic thin film materials in Examples 1 to 3 are higher, and the remanence temperature stability of the Sm-doped AlNiCo magnetic thin film materials in Examples 1 and 2 is higher.

[0073] 2) X-ray diffraction (XRD) patterns of the AlNiCo magnetic thin film materials in Example 1, Example 2 and Comparative Example 1 are as follows: Figure 7 shown.

[0074] Depend on Figure 7It can be seen that the main phase components of the AlNiCo magnetic film material in Comparative Example 1 are the FeCo-rich phase and the AlNi-rich phase obtained by the spinodal decomposition phase transformation. The introduction of the light rare earth element Sm has a certain effect on its phase transformation. Since the extremely low solid solubility of rare earth elements in the AlNiCo matrix inhibits the diffusion of other elements, it may cause the local composition to deviate from the ideal spinodal decomposition ratio, resulting in the formation of a metastable FeNi phase during annealing, and the spinodal decomposition phase strength is reduced. The increase in coercive force may be due to the pinning effect of the secondary phase and the non-magnetic barrier layer formed by Sm atoms at the grain boundary, which hinders the migration of magnetic domain walls. With regard to the temperature stability of remanence and coercive force, Sm 3+ The AlNiCo film exhibits strong uniaxial magnetocrystalline anisotropy (derived from 4f electron orbital-lattice coupling). Its doping enhances the magnetocrystalline anisotropy field, suppresses thermal perturbations of the magnetic moment at high temperatures, slows the rate of decrease in magnetization with increasing temperature, and improves the temperature stability of the remanent magnetization. Sm's strong spin-orbit coupling increases the energy barrier (ΔE) for magnetic moment reversal, suppressing the decrease in coercivity caused by thermal activation. Sm segregation at grain boundaries inhibits atomic diffusion at high temperatures, slowing the coercivity degradation caused by grain boundary migration, thus improving the temperature stability of the coercivity.

[0075] In summary, it can be seen that adding an appropriate amount of rare earth elements is beneficial to improving the comprehensive properties of AlNiCo magnetic film materials.

[0076] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A rare earth element doped AlNiCo magnetic thin film material, characterized in that: include: A silicon substrate, a silicon oxide layer, an AlNiCo film deposited on the substrate, and a metal film protective layer; wherein the AlNiCo film is doped with at least one of lanthanide elements, Sc, Sm or Y among rare earth elements to form a rare earth-doped AlNiCo magnetic film layer.

2. The rare earth element doped AlNiCo magnetic thin film material according to claim 1, characterized in that: A silicon oxide layer is located on the silicon substrate.

3. The rare earth element doped AlNiCo magnetic thin film material according to claim 1, characterized in that: The atomic percentage of rare earth elements is between 0.3% and 25%.

4. The method for preparing the rare earth element-doped AlNiCo magnetic thin film material according to any one of claims 1 to 3, characterized in that: include: 1) Cleaning high-purity single crystal silicon substrate Immerse the silicon substrate in anhydrous ethanol for ultrasonic cleaning, and dry the cleaned silicon substrate with hot air; 2) Preparation of doped metal films A multi-target co-sputtering method is used to deposit a rare earth element-doped AlNiCo thin film on a silicon substrate using a high vacuum magnetron multi-target co-sputtering system: the silicon substrate, the metal AlNiCo target, and the rare earth metal target dried in step 1) are placed in a sputtering chamber, and the sputtering chamber is evacuated. When the vacuum degree reaches the required level, argon gas is introduced and the chamber pressure is adjusted. The sputtering power, sputtering time, and target-substrate distance parameters are set to obtain a doped metal thin film sample; 3) In-situ annealing of doped metal films Performing a high vacuum in-situ heat treatment on the thin film sample prepared in step 2, evacuating the chamber, and then setting the annealing temperature and heat treatment time parameters for the heat treatment; 4) Obtaining rare earth element doped AlNiCo film After the annealing is completed, the sample is taken out after the temperature in the chamber drops below 100° C. to obtain a rare earth element-doped AlNiCo film.

5. The method for preparing a rare earth element-doped AlNiCo thin film material according to claim 4, characterized in that: In step 1), the silicon substrate is a single-sided polished high-purity single-crystalline silicon substrate with a 200nm oxide layer, a size of 0.7cm×0.7cm, a thickness of 250-500μm, a flatness of less than 3μm, and a roughness of less than 0.5nm. The silicon substrate is cleaned by ultrasonic cleaning in deionized water and ≥99.5wt% anhydrous ethanol for 60 minutes, respectively, and then dried with hot air before use immediately.

6. The method for preparing a rare earth element-doped AlNiCo thin film material according to claim 4, characterized in that: A high vacuum magnetron multi-target co-sputtering system is used to simultaneously sputter a metal aluminum nickel cobalt target and a rare earth metal target, and then a protective layer is sputtered separately. The aluminum nickel cobalt target uses a DC power supply, and the rare earth metal target uses an RF power supply. In step 2), the cleaned silicon substrate is placed on the sample stage of the sputtering chamber and on the cathode target base; the sputtering chamber is evacuated to 5×10 -4 Pa, the substrate distances between the AlNiCo target and the rare earth metal target are 5-9 cm and 5-11 cm respectively, the sputtering power of the AlNiCo target is 30w-180w, the argon flow rate is set to 24sccm-45sccm and the working pressure is maintained at 0.1Pa-1.8Pa; pre-sputtering is first carried out to remove impurities and possible oxide layers on the surface of the target, and then formal sputtering is carried out at room temperature for 15-60min.

7. The method for preparing a rare earth element-doped AlNiCo thin film material according to claim 4, characterized in that: The AlNiCo target material comprises one of AlNiCo materials of grades 1 to 9.

8. The method for preparing a rare earth element-doped AlNiCo thin film material according to claim 4, characterized in that: The thickness of the AlNiCo film is 50nm to 1000nm.

9. The method for preparing a rare earth element-doped AlNiCo thin film material according to claim 4, characterized in that: The protective layer is composed of at least one of Cr, Ti, Ta, Ru, and Ag.

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