A synergistically improved SrFeO 3-δ Method for spontaneous exchange bias effect of cubic perovskite structure

Abstract

The application discloses a kind of synergistically improves SrFeO 3‑δ Method of cubic perovskite structure spontaneous exchange bias effect relates to functional material preparation technical field.The method of the present application is by high-temperature solid-phase sintering,Er ions are doped in the Sr site of SrFeO 3‑δ Gradient magnetic Co ions are doped in the Fe site of SrFeO 3‑δ SrFeO 3‑δ Cubic perovskite structure with improved spontaneous exchange bias effect;The preparation process of the application is simple, the production cost is low, and the SrFeO 3‑δ Cubic perovskite structure prepared still can be offset along the magnetic field axis under zero magnetic field cooling condition, can realize stable unidirectional pinning effect without complex multilayer film structure or field cooling treatment, and is important to expand SrFeO 3‑δ Cubic perovskite oxide application field, improve device performance and promote the development of related scientific research.

Description

Technical Field

[0001] This invention relates to a method for synergistically improving SrFeO 3-δ The method for spontaneous exchange bias effect in cubic perovskite structures belongs to the field of functional materials preparation technology. Background Technology

[0002] The physical mechanism of conventional exchange-biased systems is typically based on a ferromagnetic (FM) / antiferromagnetic (AFM) bilayer structure, requiring the system to be cooled below the antiferromagnetic Nell temperature in the presence of an external magnetic field—a process known as field cooling. During this process, the spin structure of the antiferromagnetic layer is oriented under the influence of the external magnetic field, pinning the adjacent ferromagnetic layer. This causes a shift in the hysteresis loop along the magnetic field axis, defined as the exchange-bias field. Simultaneously, the coercivity of the system increases accordingly. Therefore, field cooling is a key external driving force for achieving unidirectional anisotropy. Based on this effect, conventional exchange-biased systems have found widespread application in spintronic devices. For example, in magnetic random access memory (MRM), this effect is used to form the pinning layer in a magnetic tunnel junction, ensuring the stability of the memory cell during write operations by fixing the magnetization direction of the reference layer. In hard disk read heads, the exchange-bias effect constitutes one of the important working mechanisms of the spin valve structure, helping to improve the read head's response sensitivity to weak magnetic fields. Furthermore, this effect has been extended to high-precision magnetic sensors, airborne magnetometers, and microwave and radio frequency devices. Typically, artificially fabricated ferromagnetic / antiferromagnetic bilayer structures are required to control magnetic moment orientation and enhance device thermal stability. However, such applications largely rely on field cooling processes or precise thin-film deposition techniques to induce and optimize the performance of the exchange bias effect, thus limiting their use.

[0003] Unlike the conventional systems described above, the spontaneous exchange bias effect refers to the phenomenon where, even under zero magnetic field cooling conditions (i.e., without any external magnetic field applied), the hysteresis loop of a system can still deflect along the magnetic field axis. The essence of this effect lies in the material's inherent spontaneous unidirectional magnetic anisotropy, with its magnetization curve exhibiting asymmetric behavior in both positive and negative magnetic field directions. This characteristic provides a novel physical basis for spintronic devices that do not require external magnetic field bias. Since this effect can achieve stable unidirectional pinning without complex multilayer structures or field cooling, it is expected to significantly simplify device manufacturing processes, reduce manufacturing costs and power consumption, and avoid the limitations imposed by field cooling processes on device integration and miniaturization. This provides a more convenient and reliable material basis for the development of high-performance, low-power, and highly integrated magnetic functional devices.

[0004] In related technologies, the regulation of SrFeO 3-δ The phase structure and magnetic properties of perovskites have been the subject of extensive fundamental research and applications, but the study of SrFeO has not been as successful. 3-δThere is limited research on the spontaneous exchange bias effect; this invention extends the understanding of SrFeO. 3-δ Perovskite oxides are of great significance in terms of application fields, improving device performance, and promoting the development of related scientific research. Summary of the Invention

[0005] To address the shortcomings of related technologies, this invention provides a method for synergistically improving SrFeO 3-δ The method of spontaneous exchange bias effect in cubic perovskite structure has the advantages of simple preparation process and low production cost, and the prepared SrFeO 3-δ The cubic perovskite structure exhibits excellent stability and spontaneous exchange bias effect, which solves the problem that conventional exchange bias effect systems rely on external magnetic fields or spin-transfer torque to set the magnetization direction of the reference layer.

[0006] The purpose of this invention is to provide a method for synergistically improving SrFeO 3-δ A method for spontaneous exchange bias effect in cubic perovskite structures, wherein the method involves high-temperature solid-state sintering in SrFeO 3-δ The Sr site is doped with rare earth element Er ions in SrFeO 3-δ The Fe site gradient doping of magnetic Co ions yields SrFeO with enhanced spontaneous exchange bias effect. 3-δ Cubic perovskite structure.

[0007] Preferably, the conditions for high-temperature solid-state sintering are as follows: two high-temperature solid-state sintering processes are adopted. The conditions for the first high-temperature solid-state sintering are: heating to 1180°C at a heating rate of 5~10°C / min, holding at that temperature for 1440 min, and then cooling at a cooling rate of 5~10°C / min. The second high-temperature solid-state sintering process is the same as the first high-temperature solid-state sintering process.

[0008] More preferably, the high-temperature solid-state sintering is carried out in an air atmosphere.

[0009] More preferably, the heating rate of the high-temperature solid-state sintering is 5°C / min, and the cooling rate is 5°C / min; the cooling method is furnace cooling.

[0010] Preferably, the SrFeO 3-δ The cubic perovskite structure is Sr 0.9 Er 0.1 Fe 1-x Co x O 3-δ Polycrystalline bulk material, where x = 0~1, and x is not 1.

[0011] More preferably, the SrFeO 3-δThe cubic perovskite structure is obtained by weighing, mixing, grinding (e.g., grinding for 120~180 min) and pressing (e.g., performing secondary pressing under uniaxial pressure, with the uniaxial pressure being 10 MPa and the holding time being 5~10 min) of SrCO3, Er2O3, Fe2O3, and CoO powders in a molar ratio, followed by high-temperature solid-state sintering.

[0012] More preferably, the SrCO3, Er2O3, Fe2O3, and CoO powders are weighed in a molar ratio of 0.9:0.1 / 2:(1-x) / 2:x / 3, where x = 0~1 and x is not 1.

[0013] Mechanism of the invention: This invention prepares Sr with a single-phase cubic perovskite structure and low oxygen vacancy concentration using a high-temperature solid-state method with a two-stage sintering process at 1180℃ / 1440min. 0.9 Er 0.1 Fe 1-x Co x O 3-δ In polycrystalline bulk materials, the solid-state sintering temperature of this invention can achieve a suitable oxygen vacancy concentration and realize Fe at the B site. 3+ / 4+ With Co 3+ / 4+ Uniform distribution of ions. SrFeO 3-δ Fe in 3+ -O 2- -Fe 3+ and Fe 4+ -O 2- -Fe 4+ Superexchange interaction gives it antiferromagnetism, and the B-site Co... 4+ The uniform incorporation of ions will lead to Fe 3+ -O 2- -Co 4+ Enhanced double exchange interactions lead to the formation of weakly ferromagnetic spin clusters, resulting in a large number of easily deflectable ferromagnetic and difficult-to-deflect antiferromagnetic layers in the polycrystalline bulk sample, thus enhancing the spontaneous exchange bias effect. This invention introduces double exchange interactions between Co magnetic ions and Fe ions to form a ferromagnetic state, thereby achieving a spontaneous exchange bias effect. Simultaneously, the cubic structure, with its low concentration of oxygen vacancies, effectively safeguards the pathways for both superexchange and double exchange interactions, maintaining a stable spontaneous exchange bias effect.

[0014] The beneficial effects of this invention are: Traditional magnetic random access memory (MRAM) relies on an external magnetic field or spin-transfer torque to set the magnetization direction of the reference layer, while Sr, which possesses a spontaneous exchange bias effect, 0.9 Er 0.1 Fe 1-x Co xO 3-δ The material (x = 0~1, and x is not 1) can be used as a self-pinning reference layer, and its magnetization direction is determined by Sr. 0.9 Er 0.1 Fe 1-x Co x O 3-δ Its own microscopic magnetic structure eliminates the need for additional writing magnetic fields or complex multilayer stacking structures. This not only simplifies the device fabrication process but also reduces writing power consumption and improves the device's thermal stability.

[0015] This invention utilizes high-temperature solid-state sintering in SrFeO 3-δ The Sr site is doped with rare earth element Er ions in SrFeO 3-δ The Fe-site gradient doping of magnetic Co ions yields Sr 0.9 Er 0.1 Fe 1-x Co x O 3-δ A series of polycrystalline bulk materials (x=0~1, and x is not 1) have been developed, achieving the fabrication of polycrystalline bulk materials with both excellent stability and spontaneous exchange bias effect. The preparation method is simple and inexpensive, utilizing a simple solid-state reaction method. This provides valuable insights for improving the development of perovskite structure-sensitive and volatile magnetic data storage devices. The polycrystalline bulk materials prepared using this method can achieve spontaneous exchange bias effect without relying on field cooling processes or thin-film deposition techniques, and are expected to be applied in the manufacturing of core spintronic devices, microwave and radio frequency devices, and general-purpose magnetic functional devices. Attached Figure Description

[0016] Figure 1 The Sr obtained in Embodiment 1 of the present invention 0.9 Er 0.1 Fe 1-x Co x O 3-δ XRD and Raman spectra of polycrystalline bulk materials Figure 1 (a) is the Sr obtained in Example 1. 0.9 Er 0.1 Fe 1-x Co x O 3-δ XRD pattern of polycrystalline bulk material Figure 1 (b) shows the Sr obtained in Example 1. 0.9 Er 0.1 Fe 1-x Co x O 3-δ Raman spectrum of polycrystalline bulk material.

[0017] Figure 2 The Sr obtained in Embodiment 1 of the present invention 0.9 Er 0.1Fe 1-x Co x O 3-δ Hysteresis loop diagram of polycrystalline bulk material at 50K under zero-field cooling Figure 2 (a) is the hysteresis loop diagram under a magnetic field of -30000Oe at 50K. Figure 2 (b) is Figure 2 (a) Enlarged view of the vicinity of zero magnetic field. Detailed Implementation

[0018] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments. In the embodiments and comparative examples of this invention, unless otherwise specified, all chemical reagents were commercially available analytical grade. The purity of the SrCO3, Er2O3, Fe2O3, and CoO powders used in the embodiments and comparative examples of this invention is ≥99%.

[0019] Example 1 A synergistic enhancement of SrFeO 3-δ The method for addressing the spontaneous exchange bias effect in cubic perovskite structures includes the following steps: SrCO3, Er2O3, Fe2O3, and CoO powder raw materials were weighed according to the ratio (molar ratio) of Sr:Er:Fe:Co=0.9:0.1 / 2:(1-x) / 2:x / 3, x=0, 0.2, 0.4, 0.6, 0.8. The mixture was then ground for 120 min, followed by a second pressing under a uniaxial pressure of 10 MPa, with each pressing holding time being 10 min, to obtain sheet-like materials. These materials were then placed in a corundum crucible for high-temperature solid-state sintering (sintering atmosphere: air). The high-temperature solid-state sintering process consisted of two stages. The first stage involved heating to 1180℃ at a heating rate of 5℃ / min and holding for 1440 min, followed by furnace cooling to room temperature at a cooling rate of 5℃ / min. The second stage involved the same process as the first high-temperature solid-state sintering to obtain SrCO3, Er2O3, Fe2O3, and CoO powder raw materials. 0.9 Er 0.1 Fe 1-x Co x O 3-δ Polycrystalline bulk material, where x = 0, 0.2, 0.4, 0.6, 0.8.

[0020] XRD patterns and Raman spectra of the polycrystalline bulk material prepared in Example 1 (see Example 1). Figure 1 XRD patterns correspond to perovskite structures; see [link to relevant documentation]. Figure 1 In (a), the Raman spectrum shows no peaks, indicating that the sample has a highly symmetrical cubic structure. See [reference needed]. Figure 1(b) From the XRD pattern and Raman spectrum, it can be seen that the polycrystalline bulk materials of Example 1 all achieved a highly symmetrical cubic perovskite structure.

[0021] Sr measured by vibrating sample magnetometer (VSM) 0.9 Er 0.1 Fe 1-x Co x O 3-δ The hysteresis loop of a polycrystalline bulk material at 50K under zero-field cooling (the polycrystalline bulk material needs to be ground into powder for measurement), i.e., without an external magnetic field applied during cooling. In the experiment, the formula is used... SEB =( CL + CR The exchange bias field is defined as ) / 2. SEB ,in CL and CR These correspond to the left and right coercive fields in the hysteresis loop, respectively. The units for the exchange bias field, left coercive field, and right coercive field are all kOe.

[0022] Tests showed that the Sr prepared in Example 1... 0.9 Er 0.1 Fe 1-x Co x O 3-δ Polycrystalline bulk powder at x=0 CL -0.3kOe, CR It is 0.209 kOe. SEB For x=0.2, the value is 0.046 kOe. CL It is -0.595 kOe. CR It is 0.494 kOe. SEB For x=0.4, the value is 0.051 kOe. CL It is -0.845 kOe. CR It is 0.665 kOe. SEB For x=0.6, the value is 0.090 kOe. CL It is -0.944 kOe. CR It is 0.763 kOe. SEBFor x=0.8, the value is 0.091 kOe. CL It is -0.398 kOe. CR It is 0.168 kOe. SEB It is 0.115 kOe.

[0023] Depend on Figure 2 (a) can be read from the polycrystalline bulk powder prepared in Example 1. SEB Value, by Figure 2 As can be seen from (b), the hysteresis loop of the polycrystalline bulk powder prepared in Example 1 exhibits a significant spontaneous exchange bias effect at 50K under zero field.

[0024] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for synergistically improving SrFeO 3-δ The method for the spontaneous exchange bias effect of cubic perovskite structures is characterized by, The method involves high-temperature solid-state sintering in SrFeO. 3-δ The Sr site is doped with rare earth element Er ions in SrFeO 3-δ The Fe site gradient doping of magnetic Co ions yields SrFeO with enhanced spontaneous exchange bias effect. 3-δ cubic perovskite structure; The conditions for high-temperature solid-state sintering are as follows: two high-temperature solid-state sintering processes are adopted. The conditions for the first high-temperature solid-state sintering are: heating to 1180°C at a heating rate of 5~10°C / min, holding at that temperature for 1440 min, and then cooling at a cooling rate of 5~10°C / min. The second high-temperature solid-state sintering process is the same as the first high-temperature solid-state sintering process.

2. The method for synergistically improving SrFeO as described in claim 1 3-δ The method for the spontaneous exchange bias effect of cubic perovskite structures is characterized by, The SrFeO 3-δ The cubic perovskite structure is Sr 0.9 Er 0.1 Fe 1-x Co x O 3-δ Polycrystalline bulk material, where x = 0~1, and x is not 1.

3. The method for synergistically improving SrFeO as described in claim 2 3-δ The method for the spontaneous exchange bias effect of cubic perovskite structures is characterized by, The SrFeO 3-δ The cubic perovskite structure is obtained by weighing, mixing, grinding, pressing, and high-temperature solid-state sintering of SrCO3, Er2O3, Fe2O3, and CoO powders in a molar ratio.

4. The method for synergistically improving SrFeO as described in claim 3 3-δ The method for the spontaneous exchange bias effect of cubic perovskite structures is characterized by, The SrCO3, Er2O3, Fe2O3, and CoO powders are weighed in a molar ratio of 0.9:0.1 / 2:(1-x) / 2:x / 3, where x = 0~1 and x is not 1.

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