Method for regulating and controlling exchange bias performance of Ni-Mn-based alloy in dual modes by changing homogenization cooling rate and aging time

Abstract

The invention discloses a method for regulating and controlling the exchange bias performance of Ni-Mn-based alloy in dual modes by changing the homogenization cooling rate and the aging time, and belongs to the technical field of functional metal materials and spintronics. The invention aims to solve the technical problems that the existing Ni-Mn-based alloy excessively depends on component adjustment in the construction of the exchange bias effect, the exchange bias field / coercive force is difficult to configure as required, and the bias level still needs to be improved. The method comprises the following steps: 1, component design and smelting; 2, pipe sealing treatment of the alloy to be subjected to heat treatment; 3, homogenizing treatment and cooling; and 4, aging treatment. The method is used for changing the homogenizing cooling rate and the aging time to regulate and control the exchange bias performance of the Ni-Mn-based alloy in the dual mode.

Description

Technical Field

[0001] This invention belongs to the field of functional metal materials and spintronics technology. Background Technology

[0002] Exchange bias (EB) refers to the unidirectional anisotropy formed at the interface between a ferromagnetic layer and an antiferromagnetic layer or a spin glass / superspin glass layer through exchange coupling. Its macroscopic characterization is the amount of displacement of the hysteresis loop along the external magnetic field axis (the exchange bias field, denoted as H). E ) and coercivity (H C Co-changes of H. E and H C The tunability reflects the evolution characteristics of interface spin configuration, exchange energy and pinning strength, and is therefore a key indicator for evaluating and designing interface magnetism. Depending on the cooling and setting methods, common paths to obtain EB include two types: zero-field cooling (ZFC) and field cooling (FC): (1) ZFC: After cooling to the target temperature without an external field, selective alignment or spontaneous bias of interface spins is induced by isothermal magnetization, light cycling or weak programming magnetic field, thereby establishing unidirectional anisotropy; (2) FC: An external field is applied and cooled in a temperature range higher than the interface spin freezing / pinning temperature, the uncompensated interface spins are directionally frozen, and the hysteresis loop produces a stable offset. The former has engineering advantages such as no need for a strong field, simplified process, low energy consumption, and easy in-situ device setting / resetting and mass production; the latter is more widely used in existing technologies, but has higher requirements for process equipment and energy consumption.

[0003] Electron nitrides (EBs) play a fundamental role in spintronic devices such as spin valves, GMR / TMR sensors, and MRAMs, as well as in magnetic coupling and energy management components. Common EB materials include traditional thin-film systems, oxide-based systems, anti-perovskite manganese nitride systems, and Heusler alloy systems. Among these systems, Ni-Mn-based Heusler alloys, through their inherent martensitic phase transformation-induced phase separation mechanism, construct stable, high-density ferromagnetic / antiferromagnetic interfaces, achieving large and stable exchange bias effects. This "self-generated" characteristic, high stability, and strong correlation with phase transitions make them a highly attractive fundamental functional material for the development of next-generation high-performance, high-density, and multifunctional spintronic devices.

[0004] However, existing technologies for Ni-Mn based Heusler alloys (EB) still have the following common problems: (1) Composition dependence and difficulty in achieving "one ratio for multiple uses": To match the H of different applications E and H CThe target EB is generally obtained by changing the chemical composition (doping / ratio), but this method leads to problems such as diverse formulations, complex adjustment, long development cycle and high production cost. In addition, the performance regulation of Ni-Mn based alloys has nonlinear characteristics, and it is difficult to quickly configure multiple properties in the same composition system, which increases the complexity and cost of manufacturing. Therefore, how to achieve efficient performance regulation without changing the basic composition is a challenge of current technological development. (2) The advantages of ZFC are not fully utilized: existing schemes mostly rely on FC to build EB, and do not pay enough attention to the construction and controllable tuning of EB under ZFC conditions, which limits the application potential of low power consumption, simple process and modular manufacturing scenarios; (3) There is still room for improvement in the achievable EB level: although some public schemes can obtain EB, the performance level is not high. Under a 2 T magnetic field, H E Typically around 50 Oe to 400 Oe, H C It is typically around 200 Oe to 800 Oe.

[0005] Existing publicly available patent examples and papers demonstrate that the above problems are widespread:

[0006] The Mn-Co-Ni-Al magnetic tape prepared by the patent "A magnetic tape with zero-field cooling exchange bias effect and its preparation method" (CN102751063A) exhibits only a single, unadjustable ZFC-EB, and its optimal H under 2 T conditions... E Approximately 818.15 Oe;

[0007] The patent “A method for preparing a shape memory alloy with exchange bias effect” (CN108277406A) is aimed at Mn-Co-Ni-Al strips, and mainly obtains different EB by changing the doping composition to prepare different alloys.

[0008] The patent “A Mn-Ni-Ga Hassler alloy material with exchange bias effect and its preparation method” (CN109321792A) uses directional solidification to obtain the bar material, which also requires composition adjustment to change the EB.

[0009] The patent “A giant exchange bias Mn-based alloy and its preparation method and application” (CN109576530A) provides multiple component modification examples for Mn-Co-Sn strips. The obtained EB still depends on multiple batches of alloy formulations, and the overall bias field is limited.

[0010] Patent "A Mn with Zero-Field Cold Exchange Bias Effect" 2-x The paper "FeCoNi Medium Entropy Alloy Material and Its Preparation Method" (CN116145008A) also obtains different entropy alloys by adjusting the Mn doping amount;

[0011] The patent "A magnetic shape memory alloy material with a large exchange bias effect and its preparation method" (CN102732762A) utilizes multiple technologies and methods, including melting, strip spinning, and single crystal growth, to prepare Mn. 50 Ni 41-x Co x Sn9 (0≤x≤5) magnetic single crystals and polycrystalline forms can also achieve different exchange bias effects by adjusting the element doping ratio, and only have field-cooled exchange bias effects.

[0012] Patent "A Mn with Zero-Field Cold Exchange Bias Effect" 2-x The paper "FeCoNi Medium Entropy Alloy Material and Its Preparation Method" (CN116145008A) also involves changing the Mn content. 2-x The Mn content in FeCoNi alloys can be adjusted to regulate the exchange coupling relationship between Mn and Mn, thereby controlling the zero-field cold exchange bias effect.

[0013] The paper "Study on Phase Transformation and Magnetic Properties of V-Doped Ni-Mn-Sn(Sb) Hassler Alloy" modifies the V content to achieve phase transformation and magnetic properties in Ni-Mn-Sn(Sb) alloys. 50 Mn 35 Sb 15-x V x In the (x=0-10) alloy, a maximum zero-field cold exchange bias field of 438 Oe was obtained;

[0014] The paper "Study on the Triggering and Mechanism of Spontaneous Exchange Bias in MnNiSnTi and NiMnInAl Heusler Alloys" achieves Ni exchange bias by substituting In with Al. 50 Mn 35 In 15-x Al x (x=0-15) The spontaneous exchange bias field in the alloy is continuously adjustable from 0-1456 Oe at 9T;

[0015] The paper "Large Exchange Bias after Zero-Field Cooling from an Unmagnetized State" achieves Ni by adjusting the V doping content. 50 Mn 50-x In x The zero-field exchange bias performance of the (x=11-15) alloy is adjustable.

[0016] In summary, the underlying principle of existing technologies is essentially static composition design. By altering the relative content of alloying elements, they directly change the ferromagnetic / antiferromagnetic coupling ratio within the material, representing a one-time design that relies on altering the material's "genes." This method cannot escape the inherent pattern of "one composition corresponding to one performance," and struggles to meet the requirement of rapidly switching between multiple H-grades within the same formulation.E and H C Indicators and stability settings requirements in ZFC / FC dual mode. Summary of the Invention

[0017] This invention aims to address the technical problems of existing Ni-Mn-based alloys in constructing the exchange bias effect, such as over-reliance on composition adjustment, difficulty in configuring the exchange bias field / coercivity as needed, and the need to improve the bias level. Instead, it provides a method for controlling the exchange bias performance of Ni-Mn-based alloys in two modes by changing the homogenization cooling rate and aging time.

[0018] A method for controlling the exchange bias properties of Ni-Mn based alloys in a dual-mode process by altering the homogenization cooling rate and aging time, comprising the following steps:

[0019] I. Composition Design and Melting:

[0020] According to the general chemical formula Ni 50-x Mn 50-y Y y X x Weigh out Ni metal, the first portion of Mn metal, Y metal and X metal according to atomic percentages. Weigh out the second portion of Mn metal at 2.0% to 5.0% of the mass of the first portion of Mn metal. Then, melt and remelt under vacuum conditions to obtain an alloy ingot.

[0021] The chemical formula Ni 50-x Mn 50-y Y y X x In the given information, x = 6~9, y = 11~12, Y is Sn, In or Sb, and X is Co or Fe;

[0022] II. Sealing treatment of the alloy to be heat-treated:

[0023] Alloy ingots, Ti sheets, and Mn sheets are placed in a single-ended open quartz tube, then vacuumed and sealed to obtain a sealed quartz tube.

[0024] III. Homogenization and Cooling:

[0025] The sealed quartz tube is placed in a heat treatment furnace for homogenization, and then air-cooled or water-quenched to obtain the homogenized and cooled alloy.

[0026] The air cooling rate described in step three is 1℃ / s to 20℃ / s; the water quenching rate described in step three is >100℃ / s.

[0027] IV. Time-sensitive processing:

[0028] The homogenized and cooled alloy is cleaned and dried, and then placed in a single-ended open quartz tube with Ti and Mn sheets, vacuumed and sealed. It is then isothermally aged for 0 to 7 days, and finally air-cooled. This completes a method for controlling the exchange bias performance of Ni-Mn based alloy in two modes by changing the homogenization cooling rate and aging time.

[0029] The air cooling rate described in step four is 0.2℃~1.0℃ / s.

[0030] The beneficial effects of this invention are:

[0031] This invention provides a composition-independent method for controlling the exchange bias effect. Within the same alloy system with a fixed chemical composition, the core objective is to controllably adjust the "amount of antiferromagnetic (AFM) coupling." The heat treatment path is programmed to actively and precisely control the strength and microstructure of the antiferromagnetic coupling, thereby achieving a wide range of controllable performance output from zero-field cold exchange bias to field-cold exchange bias. Specifically, in the homogenized and quenched sample, the rapid cooling and ordering process is suppressed, resulting in abundant anti-site defects and related AFM coupling regions. SPM clusters and short-range ordered AFM regions are highly dispersed and interpenetrating, forming an extremely high defect density SSG. In this state, the AFM coupling range is extensive and strong, making its initial exchange bias field generally greater than that of the homogenized and air-cooled sample. During subsequent aging, the ordering transformation mediated by vacancies is activated, and rapid atomic rearrangement quickly eliminates defects. The AFM region reduces energy through ordering, leading to a gradual weakening of the initially abundant AFM coupling and a subsequent decrease in EB. Because a large number of vacancies and defects remain after homogenization during quenching, the driving force for ordering is stronger. Under the same aging regime, the degree of ordering of the quenched sample is significantly improved, resulting in a lower AFM coupling and EB level after aging compared to the corresponding air-cooled sample, demonstrating high sensitivity to the aging process. Therefore, this invention achieves adjustable AFM coupling strength through a ternary combination of "homogenization cooling method (air cooling / quenching) + aging temperature + aging time," enabling the acquisition of multiple levels of designable exchange bias performance within the same composition system.

[0032] Compared with existing exchange bias materials that rely on composition adjustment, the present invention has the following significant advantages: (1) Fixed composition and adjustable performance: By designing the thermal history (homogenized cooling path and aging process), the interface spin structure and magnetic coupling state in the material can be adjusted, and multiple adjustable exchange bias fields and coercivity can be obtained without changing the chemical composition, realizing "one ratio for multiple uses"; (2) Dual compatibility of zero field cooling and field cooling: Stable EB can be established under ZFC conditions, reducing energy consumption, simplifying equipment, and having in-situ resettable characteristics. At the same time, the bias strength and controllability can be further enhanced under FC mode; (3) Strong process versatility: Applicable to a variety of Ni-Mn based alloy systems (such as Ni-Mn-Sn, Ni-Mn-In, Ni-Mn-Sb and systems doped with Co and Fe elements), with good scalability and industrialization prospects. In summary, the heat treatment method provided in this embodiment achieves structure-magnetic coupling control of the exchange bias effect of Ni-Mn based alloys without changing the chemical composition, and constructs a new approach for adjustable, multi-mode exchange bias control. Attached Figure Description

[0033] Figure 1 For the present invention to be below T B The evolution of SPM domains embedded in AFM domains under the action of an external magnetic field at (glass transition freezing temperature);

[0034] Figure 2 Example 1 Ni 44 Mn 39 Sn 11 Hysteresis loops of Co6 alloy samples after air cooling and aging treatment for 0 days (AC) at 10 K under zero field cooling and field cooling following homogenization heat treatment at 950℃ / 24h;

[0035] Figure 3 Example 1 Ni 44 Mn 39 Sn 11 Isothermal magnetization (MH) curves of Co6 alloy samples after air cooling and aging for 0 days (AC) following homogenization heat treatment at 950℃ / 24h;

[0036] Figure 4 Example 2 Ni 44 Mn 39 Sn 11 Hysteresis loops of Co6 alloy samples after quenching following homogenization heat treatment at 950℃ / 24h and aging treatment for 0 days (WQ) under zero field cooling and field cooling at 10 K.

[0037] Figure 5 Example 1 Ni 44 Mn 39 Sn 11Hysteresis loops of Co6 alloy samples after air cooling and aging treatment for 1 day (AC-1) following homogenization heat treatment at 950℃ / 24h and air cooling at 10 K;

[0038] Figure 6 Example 2 Ni 44 Mn 39 Sn 11 Hysteresis loops of Co6 alloy samples after quenching and aging treatment at 10 K under zero field cooling and field cooling, following homogenization heat treatment at 950℃ / 24h (WQ-1).

[0039] Figure 7 Example 1 Ni 44 Mn 39 Sn 11 Hysteresis loops of Co6 alloy samples after air cooling and aging treatment for 7 days (AC-7) following homogenization heat treatment at 950℃ / 24h at 10 K under zero field cooling and field cooling.

[0040] Figure 8 Example 2 Ni 44 Mn 39 Sn 11 Hysteresis loop of Co6 alloy sample after quenching and aging treatment at 10 K under zero field cooling and field cooling after homogenization heat treatment at 950℃ / 24h (WQ-7).

[0041] Figure 9 Ni in Examples 1 and 2 44 Mn 39 Sn 11 Statistics on the exchange bias field and coercivity of Co6 alloy under zero-field cooling and field cooling after different heat treatments;

[0042] Figure 10 Example 3 Ni 42 Mn 39 Sn 11 Hysteresis loops of Co8 alloy samples after air cooling and aging treatment for 0 days following homogenization heat treatment at 950℃ / 24h at 10 K under zero field cooling and field cooling.

[0043] Figure 11 Example 4 Ni 42 Mn 39 Sn 11 Hysteresis loops of Co8 alloy samples after quenching following homogenization heat treatment at 950℃ / 24h and aging treatment for 0 days (WQ) under zero field cooling and field cooling at 10 K.

[0044] Figure 12 Example 3 Ni 42 Mn 39 Sn 11Hysteresis loops of Co8 alloy samples after air cooling and aging treatment for 1 day (AC-1) following homogenization heat treatment at 950℃ / 24h and air cooling at 10 K;

[0045] Figure 13 Example 4 Ni 42 Mn 39 Sn 11 Hysteresis loops of Co8 alloy samples after quenching and aging treatment at 10 K under zero field cooling and field cooling, following homogenization heat treatment at 950℃ / 24h (WQ-1).

[0046] Figure 14 Example 3 Ni 42 Mn 39 Sn 11 Hysteresis loops of Co8 alloy samples after air cooling and aging treatment for 7 days (AC-7) following homogenization heat treatment at 950℃ / 24h at 10 K under zero field cooling and field cooling.

[0047] Figure 15 Example 4 Ni 42 Mn 39 Sn 11 Hysteresis loops of Co8 alloy samples after quenching and aging treatment at 10 K under zero field cooling and field cooling, following homogenization heat treatment at 950℃ / 24h and subsequent aging treatment (WQ-7).

[0048] Figure 16 Examples 3 and 4Ni 42 Mn 39 Sn 11 Statistics on the exchange bias field and coercivity of Co8 alloy under zero-field cooling and field cooling after different heat treatments. Detailed Implementation

[0049] Specific Implementation Method 1: This implementation method describes a method for controlling the exchange bias properties of Ni-Mn based alloys in a dual-mode approach by altering the homogenization cooling rate and aging time. It is carried out according to the following steps:

[0050] I. Composition Design and Melting:

[0051] According to the general chemical formula Ni 50-x Mn 50-y Y y X x Weigh out Ni metal, the first portion of Mn metal, Y metal and X metal according to atomic percentages. Weigh out the second portion of Mn metal at 2.0% to 5.0% of the mass of the first portion of Mn metal. Then, melt and remelt under vacuum conditions to obtain an alloy ingot.

[0052] The chemical formula Ni 50-x Mn 50-y Yy X x In the given information, x = 6~9, y = 11~12, Y is Sn, In or Sb, and X is Co or Fe;

[0053] II. Sealing treatment of the alloy to be heat-treated:

[0054] Alloy ingots, Ti sheets, and Mn sheets are placed in a single-ended open quartz tube, then vacuumed and sealed to obtain a sealed quartz tube.

[0055] III. Homogenization and Cooling:

[0056] The sealed quartz tube is placed in a heat treatment furnace for homogenization, and then air-cooled or water-quenched to obtain the homogenized and cooled alloy.

[0057] The air cooling rate described in step three is 1℃ / s to 20℃ / s; the water quenching rate described in step three is >100℃ / s.

[0058] IV. Time-sensitive processing:

[0059] The homogenized and cooled alloy is cleaned and dried, and then placed in a single-ended open quartz tube with Ti and Mn sheets, vacuumed and sealed. It is then isothermally aged for 0 to 7 days, and finally air-cooled. This completes a method for controlling the exchange bias performance of Ni-Mn based alloy in two modes by changing the homogenization cooling rate and aging time.

[0060] The air cooling rate described in step four is 0.2℃~1.0℃ / s.

[0061] The composition range in step one of this specific embodiment is within the "active region" of the EB effect. Its characteristic is that it ensures the alloy undergoes a martensitic phase transformation and forms ferromagnetic / antiferromagnetic nanoscale phase separation during subsequent heat treatment. This is the microstructural basis for generating and controlling the EB effect. Unlike conventional composition design that pursues a single optimal performance, the composition design in this specific embodiment aims to provide a design window with greater compositional tolerance.

[0062] The compensation strategy for Mn element in step one of this specific implementation method is as follows: To accurately control the final content of the key magnetic element Mn, a dynamic compensation method is adopted. That is, based on the nominal composition, an additional 2.0 wt.% to 5.0 wt.% of Mn is added, depending on the characteristics of the smelting equipment. This effectively offsets the volatilization loss under specific smelting conditions, ensuring that the ingot composition falls within the designed effective range, and guaranteeing from the source that all batches of material possess the chemical prerequisites to respond to subsequent EB control.

[0063] In steps two and four of this specific implementation method, Ti sheets and a small amount of irregular Mn sheets are placed together in a cleaned and dried single-ended open quartz tube. The Ti sheets, acting as a highly efficient getter, preferentially react with the residual trace amounts of oxygen and nitrogen in the tube at high temperatures to form stable compounds, fundamentally preventing sample oxidation. The Mn sheets, acting as a compensating source for volatile elements, will volatilize in trace amounts in a vacuum environment, forming a Mn vapor partial pressure that dynamically suppresses the volatilization loss of Mn in the sample at high temperatures. This dual protection system works together to construct a heat treatment environment with a highly stable stoichiometric ratio, ensuring the constant alloy composition before and after heat treatment. This is one of the core guarantees for achieving precise and repeatable control of EB performance.

[0064] The purpose of homogenization treatment in step three of this specific implementation method is: a. to eliminate dendritic segregation: to obtain a single austenitic parent phase with uniform composition through long-term high-temperature diffusion; b. to establish a high-temperature equilibrium state: to ensure that the alloy atoms obtain sufficient energy to reach a known and reproducible initial thermodynamic state, providing a unified starting point for all subsequent phase transformations.

[0065] In step three of this specific implementation method, cooling provides diverse defect structures and magnetic coupling precursors for aging treatment. After homogenization, one of the following two standardized cooling procedures is immediately employed to obtain two distinct initial defect structures and magnetic coupling states:

[0066] a. Air cooling: The quartz tube, after homogenization heat treatment, is quickly removed from the high-temperature furnace and immediately placed horizontally on dry refractory bricks. The entire cooling process must be carried out in a laboratory space with no forced convection and a stable ambient temperature until the quartz tube and the internal sample cool naturally to room temperature. Refractory bricks have extremely low thermal conductivity (e.g., the thermal conductivity of JM-23 type mullite lightweight insulating brick is approximately 0.18 W·m). -1 ·K -1 ~0.22W·m -1 ·K -1The quartz tube possesses excellent thermal stability, but its function is not rapid heat conduction; rather, it avoids localized rapid cooling when the quartz tube comes into contact with good conductors such as metals. This ensures that heat dissipation is primarily radiative, supplemented by natural convection, resulting in a moderate, stable, and reproducible cooling rate. By standardizing the cooling environment (refractory bricks: JM-23 type mullite lightweight insulating bricks, windless environment), this specific embodiment transforms the traditionally vague, empirical operation of air cooling into a standardized procedure with fixed parameters and predictable results. The estimated average cooling rate under these conditions (especially in the critical temperature range of martensitic transformation) is approximately 1°C / s to 20°C / s. This cooling rate is designed to allow the alloy to undergo sufficient ordered transformation, resulting in enhanced ferromagnetic coupling, reduced antiferromagnetic coupling, and the formation of a preliminary ferromagnetic / antiferromagnetic coupling separation structure. The microstructure obtained in this way responds mildly to subsequent aging treatments and is suitable for controlling moderate-intensity exchange bias effects.

[0067] b. Water quenching: A crushed quartz tube is placed directly above a quenching bath filled with room temperature deionized water, allowing the sample to be completely immersed in the water within 1 second. The extremely high cooling rate (>100℃ / s) inhibits the alloy's ordered transformation process, reduces ferromagnetic coupling within the alloy, increases antiferromagnetic coupling, and introduces high-density non-equilibrium defects such as vacancies, antisite defects, and dislocations. The resulting microstructure is in a high-energy, metastable state, making it extremely sensitive to subsequent aging treatments. During aging, the ordered transformation process using vacancies as a medium is promoted, thus providing an ideal precursor for obtaining a high-strength exchange bias effect.

[0068] The aging treatment of the alloy in step four of this specific embodiment is to further regulate the microstructure and exchange bias performance:

[0069] (1) Locking in the precursor state: For water-quenched samples, their metastable structure will relax at room temperature (such as the annihilation of supersaturated vacancies and the initial formation of atomic clusters), a process known as natural aging. After homogenization (for water-quenched samples), the samples must be aged within 24 hours to eliminate uncontrollable performance drift caused by different room temperature storage times, ensuring that the differences in the initial state of all samples are strictly limited when entering the artificial aging step, thereby guaranteeing the reproducibility of the process. This time specification is one of the key details for achieving repeatable control in this method.

[0070] (2) Sample resealing: After homogenization, the sample is ultrasonically cleaned with anhydrous ethanol, dried with a cold air blower for 30-40 seconds, and then vacuum-sealed in a quartz tube again according to the same standard described in step two. This is to provide a pure environment with no Mn loss for the aging process.

[0071] (3) Precise programming of aging process: The sample sealed in a quartz tube is placed in an aging furnace with precise temperature control (±1℃) and isothermal aging treatment is performed at 250℃~400℃ for 0 to 7 days. Then, the quartz tube that has completed the aging treatment is quickly taken out of the aging furnace and immediately placed horizontally on dry refractory bricks. The entire cooling process is consistent with the air cooling process in step three. At this time, the air cooling rate is about 0.2℃~1.0℃ / s. This specific embodiment combines the cooling method in step three with the aging temperature and time in step four to achieve the control of the degree of micro-ordering of the alloy and the AFM coupling strength of the interface, thereby realizing the control of exchange bias performance, including zero field cooling and field cooling exchange bias effects.

[0072] The basic principle of this implementation method is: combining Figure 1 The alloy initially consists of superparamagnetic (SPM) clusters embedded in an antiferromagnetic (AFM) matrix, forming a superspin glassy state (SSG). When the magnetic field is sufficiently strong, causing spin flipping at the AFM interface, the SPM clusters grow and approach each other, enhancing cluster interactions. The SPM clusters then form superferromagnetic (SFM) couplings through tunneling superexchange. The grown, stable SFM clusters then form a new SFM-AFM interface with the AFM. The SFM superspins at the interface remain below the blocking temperature (T0). B The material is "pinned" under the surface, thus inducing an exchange bias effect. Unlike the traditional "static composition design" principle, the core technology of this implementation lies in "dynamic microstructure programming." By performing different heat treatments on an alloy with a fixed composition, the material is actively guided to undergo specific, multi-stage microstructure evolution, ultimately achieving precise control over its exchange bias effect; this dynamic process is unprecedented in existing technologies.

[0073] This implementation method differs entirely from existing technologies. Its principle is dynamic microstructure reconstruction. Without altering the types and numbers of atoms, for any Ni-Mn-based alloy with a given composition, a precisely designed heat treatment "program" guides specific structural evolution within the alloy, dynamically "growing" the desired magnetic properties. EBs are stably constructed and controlled in both ZFC and FC modes, achieving multiple performance windows within the same composition to match the performance requirements and process constraints of different devices and applications. This provides a new and universal path for the engineering of Ni-Mn-based alloy EBs.

[0074] The beneficial effects of this embodiment are:

[0075] This embodiment provides a composition-independent method for controlling the exchange bias effect. Within the same alloy system with a fixed chemical composition, the core objective is to controllably adjust the "amount of antiferromagnetic (AFM) coupling." The heat treatment path is programmed to actively and precisely control the strength and microstructure of the antiferromagnetic coupling, thereby achieving a wide range of controllable performance output from zero-field cold exchange bias to field-cold exchange bias. Specifically, in the homogenized and quenched sample, the rapid cooling ordering process is suppressed, resulting in abundant anti-site defects and related AFM coupling regions. SPM clusters and short-range ordered AFM regions are highly dispersed and interpenetrating, forming an extremely high defect density SSG. In this state, the AFM coupling range is extensive and strong, making its initial exchange bias field generally greater than that of the homogenized and air-cooled sample. During subsequent aging, the ordering transformation mediated by vacancies is activated, and rapid atomic rearrangement quickly eliminates defects. The AFM region reduces energy through ordering, leading to a gradual weakening of the initially abundant AFM coupling and a subsequent decrease in EB. Because a large number of vacancies and defects remain after homogenization during quenching, the driving force for ordering is stronger. Under the same aging regime, the degree of ordering of the quenched sample is significantly improved, resulting in a lower AFM coupling and EB level after aging compared to the corresponding air-cooled sample, demonstrating high sensitivity to the aging process. Therefore, this embodiment achieves adjustable AFM coupling strength through a ternary combination of "homogenization cooling method (air cooling / quenching) + aging temperature + aging time," and can obtain multiple levels of designable exchange bias performance within the same composition system.

[0076] Compared with existing exchange bias materials that rely on composition adjustment, this embodiment has the following significant advantages: (1) Fixed composition and adjustable performance: By designing the thermal history (homogenized cooling path and aging process), the interface spin structure and magnetic coupling state in the material can be adjusted, and multiple adjustable exchange bias fields and coercivity can be obtained without changing the chemical composition, realizing "one ratio for multiple uses"; (2) Dual compatibility of zero field cooling and field cooling: Stable EB can be established under ZFC conditions, reducing energy consumption, simplifying equipment, and having in-situ resettable characteristics. At the same time, the bias strength and controllability can be further enhanced under FC mode; (3) Strong process versatility: Applicable to a variety of Ni-Mn based alloy systems (such as Ni-Mn-Sn, Ni-Mn-In, Ni-Mn-Sb and systems doped with Co and Fe elements), with good scalability and industrialization prospects. In summary, the heat treatment method provided in this embodiment achieves structure-magnetic coupling control of the exchange bias effect of Ni-Mn based alloys without changing the chemical composition, and constructs a new approach for adjustable, multi-mode exchange bias control.

[0077] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the melting described in step one is specifically performed under vacuum conditions using electric arc melting or induction melting, followed by remelting 4 to 5 times. Everything else is the same as in Specific Implementation Method One.

[0078] In this specific implementation, each ingot undergoes 4-5 remeltings. This number is set to address the characteristics of Ni-Mn-based Heusler alloys, which are prone to dendritic segregation and have difficulty controlling atomic order. The aim is to obtain highly chemically and structurally homogeneous initial ingots, thereby eliminating the interference of initial microscopic inhomogeneities on the subsequent aging treatment effect and ensuring the reproducibility and reliability of EB control.

[0079] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the alloy ingot mentioned in step two is a sheet with a length and width of 5mm~10mm and a thickness of 0.3mm~1.0mm; the alloy ingot mentioned in step two is a pre-treated alloy ingot, and the pre-treatment is carried out according to the following steps: ultrasonically cleaned sequentially with acetone, deionized water and anhydrous ethanol, and then dried by blowing with cold air for 30s~40s. Everything else is the same as in Specific Implementation Method One or Two.

[0080] The alloy ingot size range of this specific embodiment is designed to ensure that the entire sample can achieve rapid and uniform heat conduction during subsequent heat treatment, avoiding the difference in cooling rate between the core and the surface due to excessive sample thickness, thereby laying the foundation for obtaining a consistent phase separation structure and EB properties.

[0081] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the thickness of the Ti sheet mentioned in steps two and four is 0.05mm to 0.1mm; and the mass of the Mn sheet mentioned in steps two and four is 0.3g to 1.0g. Everything else is the same as in Specific Implementation Methods One to Three.

[0082] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the outer diameter of the single-end open quartz tube described in steps Two and Four is 16mm~23mm, the wall thickness is 1mm~1.5mm, and the length is 150mm~200mm. Everything else is the same as in Specific Implementation Methods One to Four.

[0083] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the single-end open quartz tubes mentioned in steps two and four are pre-treated single-end open quartz tubes. The pretreatment is carried out according to the following steps: first, soaking and cleaning with a 2%~5% HF solution (by volume) for 12h~24h; then soaking in deionized water for 24h~36h, changing the deionized water 2~3 times during the soaking period; finally, drying at a temperature of 80℃~100℃ for 12h~24h. Everything else is the same as in Specific Implementation Methods One to Five.

[0084] The purpose of this specific implementation is to thoroughly remove residual metal ions and impurities from the inner wall of the quartz tube, preventing them from volatilizing and contaminating the alloy sample during high-temperature heat treatment. An ultra-clean environment is crucial for ensuring the purity of the alloy surface and preventing abnormal oxidation or nitriding. This is essential for precisely controlling the microstructural evolution of the alloy body (rather than the surface contamination layer) during subsequent aging treatment.

[0085] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that the vacuuming described in steps two and four is specifically performed as follows: Connect the open end of the quartz tube to the vacuum device, evacuate until the vacuum level inside the quartz tube reaches 1.2 Pa to 1.5 Pa, introduce argon gas into the quartz tube to 0.9 atm to 1.1 atm, and repeat the vacuuming process 4 to 5 times until the vacuum level inside the quartz tube reaches 0.8 Pa to 1.0 Pa. Further evacuate using a liquid nitrogen cold trap until the vacuum level reaches 1.2 × 10⁻⁶ Pa. -5 Pa ~ 1.5 × 10 -5 Pa, and finally close the vent valve. Everything else is the same as in embodiments one through six.

[0086] In this specific embodiment, the ultra-high vacuum environment eliminates thermal convection and conduction of air molecules to the greatest extent, so that the subsequent air cooling process mainly depends on the radiative heat transfer between the sample and the quartz tube wall, which greatly improves the controllability and reproducibility of the air cooling step.

[0087] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the homogenization treatment in step three specifically involves placing the sealed quartz tube in a heat treatment furnace at 950℃~1000℃ and holding it at that temperature for 24h~36h. Everything else is the same as in Specific Implementation Methods One to Seven.

[0088] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: in step three, within 3 seconds after homogenization treatment, the homogenized quartz tube is air-cooled or water-quenched; specifically, the air cooling in steps three and four involves placing the quartz tube horizontally on dry refractory bricks and then air-cooling it to room temperature in a windless environment before finally breaking the quartz tube; specifically, the water quenching in step three involves placing the quartz tube above a quenching tank filled with room temperature deionized water, then breaking the quartz tube, and the alloy is completely immersed in the deionized water within 1 second. Everything else is the same as in Specific Implementation Methods One to Eight.

[0089] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: the cleaning described in step four specifically involves ultrasonic cleaning with anhydrous ethanol, followed by drying with cold air for 30-40 seconds; the isothermal aging treatment described in step four specifically involves isothermal aging at a temperature of 250℃-400℃ for 0-7 days. Everything else is the same as in Specific Implementation Methods One to Nine.

[0090] The beneficial effects of the present invention are verified using the following embodiments:

[0091] Example 1:

[0092] A method for controlling the exchange bias properties of Ni-Mn based alloys in a dual-mode process by altering the homogenization cooling rate and aging time, comprising the following steps:

[0093] I. Composition Design and Melting:

[0094] According to the chemical formula Ni 44 Mn 39 Sn 11 The atomic percentages of Co6 are determined by weighing Ni metal, the first portion of Mn metal, Sn metal and Co metal, and the second portion of Mn metal is weighed at 3.0% of the mass of the first portion of Mn metal. The mixture is then arc-melted and remelted 5 times under vacuum conditions to obtain an alloy ingot.

[0095] II. Sealing treatment of the alloy to be heat-treated:

[0096] Alloy ingots, Ti sheets, and Mn sheets are placed in a single-ended open quartz tube, then vacuumed and sealed to obtain a sealed quartz tube.

[0097] The alloy ingot is a sheet with a length and width of 10mm and a thickness of 1.0mm; the alloy ingot is a pre-treated alloy ingot, and the pre-treatment is carried out according to the following steps: ultrasonically cleaned with acetone, deionized water and anhydrous ethanol in sequence, and then dried by blowing cold air for 30 seconds.

[0098] III. Homogenization and Cooling:

[0099] The sealed quartz tube was placed in a heat treatment furnace at 950℃ and kept at that temperature for 24 hours to obtain a homogenized quartz tube. Within 3 seconds after homogenization, the homogenized quartz tube was air-cooled to obtain a homogenized and cooled alloy.

[0100] The air cooling process described in step three involves placing the homogenized quartz tube horizontally on dry refractory bricks (JM-23 type mullite lightweight insulating bricks), then air cooling it to room temperature in a windless environment, and finally breaking the quartz tube. The cooling rate of the air cooling is approximately 1℃ / s to 10℃ / s.

[0101] IV. Time-sensitive processing:

[0102] The homogenized and cooled alloy is cleaned, and then placed in a single-ended open quartz tube with Ti and Mn sheets, vacuumed and sealed. Then, it is isothermally aged for 0 days, 1 day or 7 days at 250℃, and finally air-cooled. This completes a method for controlling the exchange bias performance of Ni-Mn based alloy in two modes by changing the homogenization cooling rate and aging time.

[0103] The air cooling described in step four specifically involves placing the isothermal aging treated quartz tube horizontally on dry refractory bricks (JM-23 type mullite lightweight insulating bricks), then air cooling it to room temperature in a windless environment, and finally breaking the quartz tube; the cooling rate of the air cooling is approximately 0.2℃ / s~0.5℃ / s.

[0104] The thickness of the Ti sheet mentioned in steps two and four is 0.1 mm; the mass of the Mn sheet mentioned in steps two and four is 0.5 g.

[0105] The single-ended open quartz tube mentioned in steps two and four has an outer diameter of 18 mm, a wall thickness of 1 mm, and a length of 200 mm.

[0106] The single-ended quartz tube mentioned in step two is a pre-treated single-ended quartz tube, and the pretreatment is carried out according to the following steps: first, soak and clean it with HF solution with a volume percentage of 2% for 24 hours, then soak it in deionized water for 24 hours, and change the deionized water 3 times during the soaking period, and finally dry it at a temperature of 80°C for 24 hours.

[0107] The vacuuming described in steps two and four is specifically performed as follows: Connect the open end of the quartz tube to the vacuum device, evacuate the tube until the vacuum level reaches 1.2 Pa, introduce argon gas into the tube to 1.1 atm, and repeat the vacuuming process five times until the vacuum level reaches 1.0 Pa. Then, further evacuate the tube using a liquid nitrogen cold trap until the vacuum level reaches 1.5 × 10⁻⁶ Pa. -5 Pa, and finally close the vent valve.

[0108] The cleaning process described in step four involves ultrasonic cleaning with anhydrous ethanol followed by drying with cold air for 30 seconds.

[0109] Example 2: This example differs from Example 1 in that: in step 3, the homogenized quartz tube is water-quenched within 3 seconds after homogenization; specifically, the homogenized quartz tube is placed above a quenching tank filled with room temperature deionized water, and then the quartz tube is broken, with the alloy completely immersed in the deionized water within 1 second; the cooling rate of the water quenching is >100℃ / s. Everything else is the same as in Example 1.

[0110] Example 3: This example differs from Example 1 in that the chemical formula Ni in step 1... 42 Mn 39 Sn 11 Co8. Everything else is the same as in Example 1.

[0111] Example 4: This example differs from Example 2 in that the chemical formula Ni in step 1... 42 Mn 39 Sn 11 Co8. Everything else is the same as in Example 2.

[0112] Figure 2 Example 1 Ni 44 Mn 39 Sn 11 The hysteresis loops of Co6 alloy samples after homogenization heat treatment at 950℃ / 24h, followed by air cooling and aging for 0 days (AC), are shown at 10 K under both zero-field and field cooling conditions. It can be seen that the alloy exhibits an exchange bias effect under both zero-field and field cooling conditions at 10 K after this heat treatment, meaning the hysteresis loop is shifted along the magnetic field axis. The two intersections with the magnetic field axis when the magnetization is zero are denoted as H1 and H2, respectively, and the exchange bias field H... E = -(H1+H2) / 2, coercivity H C =|H1-H2| / 2. In the diagram, under zero-field cooling conditions: H1 = -2519.4 Oe, H2 = 900.6 Oe, H... E =809.4 Oe, H C =1710.0 Oe. Under field cooling conditions: H1 = -1060.2 Oe, H2 = -171.0 Oe, H E =615.6 Oe, H C =444.6 Oe.

[0113] Figure 3 Example 1 Ni 44 Mn 39 Sn 11The isothermal magnetization (MH) curves of Co6 alloy samples after homogenization heat treatment at 950℃ / 24h followed by air cooling and aging for 0 days (AC) at 200K are shown in the figure. As can be seen from the figure, at the freezing temperature, the alloy is in a superparamagnetic (SPM) martensite state. The magnetization increases monotonically with the applied magnetic field, and the overall curve exhibits a smooth S-shape, showing an almost symmetrical nonlinear response in both positive and negative magnetic field regions. The curve shows no obvious hysteresis or coercivity, indicating that the magnetic moments can freely flip under thermal fluctuations, and there is no stable ferromagnetic domain structure. In the low magnetic field region, the magnetization is approximately linearly related to the magnetic field; as the magnetic field increases, the magnetization gradually deviates from linearity and transitions towards saturation, consistent with the superparamagnetic nanocluster magnetization behavior described by the Langevin function.

[0114] Figure 4 Example 2 Ni 44 Mn 39 Sn 11 The hysteresis loops of Co6 alloy samples after homogenization heat treatment at 950℃ / 24h, followed by quenching and aging for 0 days (WQ) at 10 K under both zero-field and field cooling conditions. It can be seen that this alloy exhibits an exchange bias effect under both zero-field and field cooling conditions at 10 K after homogenization heat treatment and quenching. Under zero-field cooling conditions, H1 = -2767.6 Oe, H2 = 757.6 Oe, H... E =1005.0 Oe, H C =1762.6 Oe. Under field cooling conditions: H1 = -1117.2 Oe, H2 = -142.5 Oe, H E =629.9 Oe, H C =487.4 Oe.

[0115] Figure 5 Example 1 Ni 44 Mn 39 Sn 11 The hysteresis loops of Co6 alloy samples after homogenization heat treatment at 950℃ / 24h followed by air cooling and aging for 1 day (AC-1) under zero-field cooling and field cooling at 10 K are shown. It can be seen that the alloy exhibits exchange bias effects under both zero-field cooling and field cooling conditions at 10 K after homogenization heat treatment followed by air cooling and aging for 1 day. Under zero-field cooling conditions, H1 = -2473.8 Oe, H2 = 877.8 Oe, H... E =798.0 Oe, H C =1675.8 Oe. Under field cooling conditions: H1 = -1037.4 Oe, H2 = -182.4 Oe, H E =609.9 Oe, H C =427.5 Oe.

[0116] Figure 6Example 2 Ni 44 Mn 39 Sn 11 The hysteresis loops of Co6 alloy samples after homogenization heat treatment at 950℃ / 24h, quenching, and aging for 1 day (WQ-1) under zero-field cooling and field cooling at 10 K are shown. It can be seen that this alloy exhibits exchange bias effects under both zero-field cooling and field cooling conditions at 10 K after homogenization heat treatment, quenching and cooling, and aging for 1 day. Under zero-field cooling conditions, H1 = -2449.0 Oe, H2 = 877.8 Oe, H... E =785.6 Oe, H C =1663.4 Oe. Under field cooling conditions: H1 = -998.1 Oe, H2 = -200.4 Oe, H E =599.3 Oe, H C =398.9 Oe.

[0117] Figure 7 Example 1 Ni 44 Mn 39 Sn 11 The hysteresis loops of Co6 alloy samples after homogenization heat treatment at 950℃ / 24h followed by air cooling and aging for 7 days (AC-7) at 10 K under both zero-field cooling and field cooling conditions. It can be seen that the alloy exhibits an exchange bias effect under both zero-field cooling and field cooling conditions at 10 K after homogenization heat treatment followed by air cooling and aging for 7 days. Under zero-field cooling conditions, H1 = -2394.0 Oe, H2 = 899.6 Oe, H... E =747.2 Oe, H C =1646.8 Oe. Under field cooling conditions: H1 = -979.8 Oe, H2 = -189.4 Oe, H E =584.6 Oe, H C =395.2 Oe.

[0118] Figure 8 Example 2 Ni 44 Mn 39 Sn 11 The hysteresis loops of Co6 alloy samples after homogenization heat treatment at 950℃ / 24h, quenching, and aging for 7 days (WQ-7) under zero-field cooling and field cooling at 10 K are shown. It can be seen that this alloy exhibits an exchange bias effect under both zero-field cooling and field cooling conditions at 10 K after homogenization heat treatment, quenching, cooling, and aging for 7 days. Under zero-field cooling conditions, H1 = -2376.2 Oe, H2 = 900.1 Oe, H... E =738.1 Oe, H C=1638.2 Oe. Under field cooling conditions: H1 = -959.6 Oe, H2 = -175.6 Oe, H E =567.6 Oe, H C =392.0 Oe.

[0119] Figure 9 Ni in Examples 1 and 2 44 Mn 39 Sn 11 Statistical analysis of the exchange bias field and coercivity of Co6 alloy under zero-field cooling and field cooling after different heat treatments. It can be seen that, through different heat treatments, the H... E Adjustable between 738.1 Oe and 1005.0 Oe, with a range up to 266.9 Oe, and a relative minimum amplitude of 36.16%. C Adjustable between 1638.2 Oe and 1762.6 Oe, with a range up to 124.4 Oe and a relative minimum amplitude of 7.59%. Under field cooling, H... E Adjustable between 567.6 Oe and 629.9 Oe, with a range up to 62.3 Oe, and a relative minimum amplitude of 10.98% (relative minimum). H C It is adjustable between 392.0 Oe and 487.4 Oe, with a range of up to 95.4 Oe and a relative minimum value range of 24.3%.

[0120] Figure 10 Example 3 Ni 42 Mn 39 Sn 11 The hysteresis loops of Co8 alloy samples after air cooling and aging for 0 days (AC) at 10 K under both zero-field and field cooling following homogenization heat treatment at 950℃ / 24h. It can be seen that the alloy exhibits an exchange bias effect under both zero-field and field cooling conditions at 10 K after this heat treatment, i.e., the hysteresis loop is shifted along the magnetic field axis. Under zero-field cooling conditions: H1 = -1311.0 Oe, H2 = 695.4 Oe, H... E =307.8 Oe, H C =1003.2 Oe. Under field cooling conditions: H1=-1024.6 Oe, H2=171.0 Oe, H E =426.8 Oe, H C =597.8 Oe.

[0121] Figure 11 Example 4 Ni 42 Mn 39 Sn 11The hysteresis loops of Co8 alloy samples after homogenization heat treatment at 950℃ / 24h, followed by quenching and aging for 0 days (WQ) at 10 K under both zero-field cooling and field cooling conditions. It can be seen that this alloy exhibits an exchange bias effect under both zero-field cooling and field cooling conditions at 10 K after homogenization heat treatment and quenching. Under zero-field cooling conditions, H1 = -1379.4 Oe, H2 = 638.4 Oe, H... E =370.5 Oe, H C =1008.9 Oe. Under field cooling conditions: H1 = -1046.0 Oe, H2 = 163.8 Oe, H E =441.1 Oe, H C =604.9 Oe.

[0122] Figure 12 Example 3 Ni 42 Mn 39 Sn 11 The hysteresis loops of Co8 alloy samples after homogenization heat treatment at 950℃ / 24h followed by air cooling and aging for 1 day (AC-1) under zero-field cooling and field cooling at 10 K are shown. It can be seen that the alloy exhibits exchange bias effects under both zero-field cooling and field cooling conditions at 10 K after homogenization heat treatment followed by air cooling and aging for 1 day. Under zero-field cooling conditions, H1 = -1174.2 Oe, H2 = 645.4 Oe, H... E =264.4 Oe, H C =909.8 Oe. Under field cooling conditions: H1 = -1003.2 Oe, H2 = 158.0 Oe, H E =422.6 Oe, H C =580.6 Oe.

[0123] Figure 13 Example 4 Ni 42 Mn 39 Sn 11 The hysteresis loops of Co8 alloy samples after homogenization heat treatment at 950℃ / 24h, quenching, and aging for 1 day (WQ-1) under zero-field cooling and field cooling at 10 K are shown. It can be seen that this alloy exhibits exchange bias effects under both zero-field cooling and field cooling conditions at 10 K after homogenization heat treatment, quenching and cooling, and aging for 1 day. Under zero-field cooling conditions, H1 = -1151.4 Oe, H2 = 627.0 Oe, H... E =262.2 Oe, H C =889.2 Oe. Under field cooling conditions: H1 = -957.6 Oe, H2 = 205.2 Oe, H E =376.2 Oe, H C =581.4 Oe.

[0124] Figure 14 Example 3 Ni 42 Mn 39 Sn 11 The hysteresis loops of Co8 alloy samples after homogenization heat treatment at 950℃ / 24h followed by air cooling and aging for 7 days (AC-7) at 10 K under both zero-field cooling and field cooling conditions. It can be seen that the alloy exhibits an exchange bias effect under both zero-field cooling and field cooling conditions at 10 K after homogenization heat treatment followed by air cooling and aging for 7 days. Under zero-field cooling conditions, H1 = -1094.4 Oe, H2 = 581.4 Oe, H... E =256.5 Oe, H C =837.9 Oe. Under field cooling conditions: H1 = -855.0 Oe, H2 = 205.2 Oe, H E =324.9 Oe, H C =530.1 Oe.

[0125] Figure 15 Example 4 Ni 42 Mn 39 Sn 11 The hysteresis loops of Co8 alloy samples after homogenization heat treatment at 950℃ / 24h, quenching, and aging for 7 days (WQ-7) under zero-field cooling and field cooling at 10 K are shown. It can be seen that this alloy exhibits an exchange bias effect under both zero-field cooling and field cooling conditions at 10 K after homogenization heat treatment, quenching, cooling, and aging for 7 days. Under zero-field cooling conditions, H1 = -946.2 Oe, H2 = 615.6 Oe, H... E =165.3 Oe, H C =780.9 Oe. Under field cooling conditions: H1 = -775.2 Oe, H2 = -144.0 Oe, H E =315.6 Oe, H C =459.6 Oe.

[0126] Figure 16 Examples 3 and 4Ni 42 Mn 39 Sn 11 Statistical analysis of the exchange bias field and coercivity of Co8 alloy under zero-field cooling and field cooling after different heat treatments. It can be seen that, through different heat treatments, H... E Adjustable between 165.3 Oe and 370.5 Oe, with a variation range of up to 205.2 Oe, and a relative minimum amplitude of 124.1%. CAdjustable between 780.9 Oe and 1008.9 Oe, with a variation range of up to 228.0 Oe and a relative minimum amplitude of 29.2%. Under field cooling, H... E Adjustable between 315.6 Oe and 441.1 Oe, with a variation range of up to 125.5 Oe, and a relative minimum amplitude of 39.8% (relative minimum). H C It is adjustable between 459.6 Oe and 604.9 Oe, with a variation range of up to 145.3 Oe and a relative minimum value range of 31.6%.

Claims

1. A method for changing the exchange bias performance of a Ni-Mn-based alloy in a dual-mode under the regulation of homogenization cooling rate and aging time, characterized in that It is carried out in the following steps: I. Component design and smelting: According to the chemical formula Ni 50-x Mn 50-y Y y X x The atomic percentage of Ni metal, the first Mn metal, Y metal and X metal is taken, the second Mn metal is taken according to 2.0%-5.0% of the mass of the first Mn metal, then the melting and remelting are carried out under vacuum condition, and the alloy ingot is obtained. The chemical formula Ni 50-x Mn 50-y Y y X x x=6~9, y=11~12, Y is Sn, In or Sb, X is Co or Fe II. Sealed tube treatment of the alloy to be heat treated: Place the alloy ingot, Ti sheet and Mn sheet in a single-end open quartz tube, then vacuumize and seal to obtain the sealed quartz tube; III. Homogenization treatment and cooling: Place the sealed quartz tube in a heat treatment furnace for homogenization treatment, then perform air cooling or water quenching to obtain the alloy after homogenization treatment and cooling; The cooling speed of air cooling in step III is 1℃ / s~20℃ / s; the cooling speed of water quenching in step III is >100℃ / s; IV. Aging treatment: Wash and dry the alloy after homogenization treatment and cooling, then place it together with the Ti sheet and Mn sheet in a single-end open quartz tube, vacuumize and seal, then isothermal age for 0 days~7 days, and finally perform air cooling, thereby completing the method for changing the exchange bias performance of Ni-Mn-based alloy in dual-mode under the regulation of homogenization cooling rate and aging time; The cooling speed of air cooling in step IV is 0.2℃~1.0℃ / s.

2. The method of claim 1, wherein the method is characterized in that The smelting in step I is arc smelting or induction smelting under vacuum condition, and the remelting is performed 4~5 times.

3. The method of claim 1, wherein the method is characterized in that The alloy ingot in step II is a sheet with a length and width of 5mm~10mm and a thickness of 0.3mm~1.0mm; the alloy ingot in step II is a pretreated alloy ingot, and the pretreatment is carried out in the following steps: sequentially ultrasonic clean with acetone, deionized water and anhydrous ethanol, and then dry with cold wind for 30s~40s.

4. The method of claim 1, wherein the method is characterized in that The thickness of the Ti sheet in steps II and IV is 0.05mm~0.1mm; the mass of the Mn sheet in steps II and IV is 0.3g~1.0g.

5. The method of claim 1, wherein the method is characterized in that The single-end open quartz tube in steps II and IV has an outer diameter of 16mm~23mm, a wall thickness of 1mm~1.5mm, and a length of 150nm~200mm.

6. The method of claim 1, wherein the method is characterized in that the homogenization cooling rate and aging time are adjusted to control the exchange bias performance of the Ni-Mn-based alloy in the dual-mode. The single-end open quartz tube in steps II and IV is a pretreated single-end open quartz tube, and the pretreatment is carried out in the following steps: first soak clean with HF solution with a volume percentage of 2%~5% for 12h~24h, then soak with deionized water for 24h~36h, and replace the deionized water 2~3 times during the soaking, and finally dry at a temperature of 80℃~100℃ for 12h~24h.

7. The method for controlling the exchange bias properties of Ni-Mn based alloys in dual modes by changing the homogenization cooling rate and aging time according to claim 1, characterized in that... The vacuumizing in the second step and the fourth step is specifically carried out in the following steps: connecting the open end of the quartz tube with the vacuum device, carrying out the air extraction treatment until the vacuum degree in the quartz tube reaches 1.2 Pa~1.5 Pa, introducing argon into the quartz tube to 0.9 atm~1.1 atm, opening the vacuum device again to carry out the vacuumizing treatment cycle 4~5 times, until the vacuum degree in the quartz tube reaches 0.8 Pa~1.0 Pa, further extracting the air through the liquid nitrogen cold trap, until the vacuum degree reaches 1.2×10 - 5 Pa~1.5×10 -5 Pa, and finally closing the air valve.

8. The method for controlling the exchange bias properties of Ni-Mn based alloys in dual modes by changing the homogenization cooling rate and aging time according to claim 1, characterized in that... The homogenization treatment in step III is specifically placing the sealed quartz tube in a heat treatment furnace at 950℃~1000℃ and holding for 24h~36h.

9. The method of claim 1, wherein the method is characterized in that the homogenization cooling rate and aging time are regulated to change the exchange bias performance of the Ni-Mn-based alloy in the dual-mode. Air cooling or water quenching is performed on the homogenized quartz tube within 3s after the homogenization treatment in step III; the air cooling in steps III and IV is specifically placing the quartz tube horizontally on dry refractory bricks, then air cooling to room temperature in a windless environment, and finally breaking the quartz tube; the water quenching in step III is specifically placing the quartz tube above the quenching tank of deionized water at room temperature, then breaking the quartz tube, and the alloy is completely immersed in the deionized water within 1s.

10. The method of claim 1, wherein the method is characterized in that the homogenization cooling rate and aging time are adjusted to control the exchange bias performance of the Ni-Mn-based alloy in the dual-mode. The cleaning and drying in step four is specifically ultrasonic cleaning with anhydrous ethanol, and then drying with cold air for 30s~40s; the isothermal aging treatment in step four is specifically isothermal aging treatment for 0 days~7 days at a temperature of 250℃~400℃. ​

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