Preparation method of Fe3BO6 material with strong spontaneous exchange bias effect at room temperature

Abstract

The present invention discloses a method for preparing an Fe3BO6 material having a strong spontaneous exchange bias effect at room temperature. The method comprises weighing high-purity boric acid powder and nano-sized α-Fe2O3 powder according to the atomic percentage of Fe3BO6, uniformly mixing the two, and then subjecting the uniformly mixed powder sample to a two-step high-temperature solid-phase reaction in an air atmosphere, wherein the maximum reaction temperature is controlled within a temperature range of 750°C to 860°C. The material is then naturally cooled to room temperature to obtain the Fe3BO6 powder material. The preparation method of the Fe3BO6 material of the present invention is simple and low-cost, exhibits a strong spontaneous exchange bias effect in the temperature range of 50 K to 350 K, and particularly exhibits a strong spontaneous exchange bias effect at room temperature of 300 K, which is conducive to practical technical applications.

Description

Technical Field

[0001] The present invention relates to the field of preparation of magnetic functional materials, and in particular to a method for preparing Fe3BO6 material with a strong spontaneous exchange bias effect at room temperature. Background Art

[0002] The phenomenon of a hysteresis loop deviating from the magnetic field axis is called exchange bias, also known as unidirectional anisotropy. In 1956, Meiklejohn and Bean first discovered exchange bias in Co / CoO nanoparticles by applying an external magnetic field and then cooling the material. This phenomenon is known as the ordinary exchange bias effect. In 2011, Wang et al. discovered that in NiMnIn alloys, exchange bias can be generated in the system simply by initial magnetization, without the need for an external magnetic field. Cooling the material to below its phase transition temperature without applying a magnetic field can generate exchange bias. This phenomenon was later referred to as the spontaneous exchange bias effect.

[0003] The exchange bias effect, considered a cornerstone of spintronic device design and widely used in magnetic memory devices, plays a crucial role in the current and future development and application of spintronics. When designing spintronic devices based on giant magnetoresistance (GMR) and tunneling magnetoresistance (TMR), it is unavoidable to pin the ferromagnetic layer in a fixed direction. This is achieved through the exchange bias effect, making the exchange bias effect promising for applications in ultra-high-density magnetic recording, spin valves, and other spintronic devices. The spontaneous exchange bias effect does not require heating or cooling the magnetic field, making it more convenient and controllable in device applications. A simple method for preparing a low-cost material with strong spontaneous exchange bias at room temperature would greatly advance the application of the exchange bias effect in spintronic devices. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing Fe3BO6 material with strong spontaneous exchange bias effect at room temperature, so as to realize the preparation of material with strong spontaneous exchange bias effect at room temperature in a simple and low-cost manner.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing Fe3BO6 material with strong spontaneous exchange bias effect at room temperature, characterized in that it comprises the following steps:

[0006] 1) Weigh boric acid powder and nano-sized α-Fe2O3 powder according to the atomic percentage of Fe3BO6;

[0007] 2) Evenly mix boric acid powder and nano-sized α-Fe2O3 powder;

[0008] 3) The uniformly mixed powder sample was heated to 670°C in an air atmosphere and kept at this temperature for 48 hours to carry out the first step of high-temperature solid-phase reaction;

[0009] 4) Continue heating to 750°C~860°C in air atmosphere and keep warm for 24 hours to carry out the second step of high temperature solid phase reaction;

[0010] 5) The obtained sample is naturally cooled to room temperature to obtain Fe3BO6 powder material.

[0011] In a preferred embodiment, in step 1), the purity of the boric acid powder and the nano-sized α-Fe2O3 powder is controlled at 99.5% to 99.99%.

[0012] In a preferred embodiment, in step 1), the average particle size of the nano-sized α-Fe2O3 powder is in the range of 30 nm to 50 nm.

[0013] In a preferred embodiment, in step 3), the heating rate of the first high-temperature solid-phase reaction is 5°C / min.

[0014] In a preferred embodiment, in step 4), the heating rate of the second high-temperature solid-phase reaction is 2°C / min.

[0015] In a preferred embodiment, in step 4), the holding temperature of the second high-temperature solid-phase reaction is 750°C.

[0016] In a preferred embodiment, in step 5), the sample is cooled in a furnace or naturally cooled in the air.

[0017] The present invention provides a method for preparing a Fe3BO6 material with a strong spontaneous exchange bias effect at room temperature. By adopting the above method, the following beneficial effects are achieved:

[0018] (1) The Fe3BO6 material prepared by the method proposed in this application exhibits a strong spontaneous exchange bias effect in the temperature range of 50 K to 350 K;

[0019] (2) The preparation method of the present invention is simple, easy to implement, low in cost, and is conducive to industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings, embodiments and comparative examples:

[0021] Figure 1 This is the X-ray diffraction pattern of the Fe3BO6 material of Example 1 of the present invention.

[0022] Figure 2 The Fe3BO6 powder material of Example 1 of the present invention at 300 K isM - H curve chart.

[0023] Figure 3 The Fe3BO6 powder material of Example 1 of the present invention at 350 K M - H curve chart.

[0024] Figure 4 The Fe3BO6 powder material of Example 1 of the present invention at 200 K is M - H curve chart.

[0025] Figure 5 The Fe3BO6 powder material of Example 1 of the present invention at 100 K is M - H curve chart.

[0026] Figure 6 The Fe3BO6 powder material of Example 1 of the present invention at 50 K is M - H curve chart.

[0027] Figure 7 This is the X-ray diffraction pattern of the Fe3BO6 material of Example 2 of the present invention.

[0028] Figure 8 The Fe3BO6 powder material of Example 2 of the present invention at 300 K is M - H curve chart.

[0029] Figure 9 It is the X-ray diffraction pattern of the Fe3BO6 material of the comparative example of the present invention.

[0030] Figure 10 The Fe3BO6 material of the comparative example of the present invention at 300 K M - H curve chart. DETAILED DESCRIPTION

[0031] Example 1:

[0032] First, according to the atomic percentage of Fe3BO6, nano-scale α-Fe2O3 powder with a purity of 99.5% and boric acid powder with a purity of 99.99%, where the average particle size of the α-Fe2O3 powder was 30 nm, were weighed. The high-purity boric acid powder and nano-scale α-Fe2O3 powder were then uniformly mixed. The uniformly mixed powder sample was then heated to 670°C at a heating rate of 5°C / min in air atmosphere and kept at this temperature for 48 hours to carry out the first high-temperature solid-phase reaction. The temperature was further increased to 750°C at a heating rate of 2°C / min in air atmosphere and kept at this temperature for 24 hours to carry out the second high-temperature solid-phase reaction. Finally, the obtained sample was cooled to room temperature by natural furnace cooling to obtain Fe3BO6 powder material.

[0033] like Figure 1 The figure shows the XRD pattern of the Fe3BO6 powder sample obtained in Example 1. As can be seen from the figure, the main characteristic peaks of the XRD of the obtained sample correspond to the characteristic peaks of the standard card ICDD 01-070-0880, indicating that the prepared powder material is indeed Fe3BO6.

[0034] Figure 2 This is the hysteresis loop of Fe3BO6 powder measured directly at 300 K. M - H The graph shows that the resulting Fe3BO6 exhibits a strong exchange bias effect, with the corresponding exchange bias field reaching approximately 4234 Oe. Since the test process did not involve any heating or cooling of the magnetic field, this phenomenon is attributed to a spontaneous exchange bias effect.

[0035] like Figures 3 to 6 As shown in Figure 3, from 350 K to 50 K, as the temperature changes, we can observe that the obtained Fe3BO6 samples can all exhibit a strong spontaneous exchange bias effect, and the exchange bias field gradually increases from about 3593 Oe to about 4982 Oe.

[0036] Example 2:

[0037] First, based on the atomic percentage of Fe3BO6, nano-scale α-Fe2O3 powder with a purity of 99.5% and boric acid powder with a purity of 99.99%, where the average particle size of the α-Fe2O3 powder is 30 nm, were weighed. The high-purity boric acid powder and nano-scale α-Fe2O3 powder were then uniformly mixed. The uniformly mixed powder sample was then heated to 670°C at a heating rate of 5°C / min in an air atmosphere and kept at this temperature for 48 hours to carry out the first high-temperature solid-phase reaction.

[0038] Unlike Example 1, Example 2 continued to heat the sample to 860°C at a rate of 2°C / min in an air atmosphere, and the temperature was maintained for 24 hours to perform the second high-temperature solid-phase reaction. Finally, the resulting sample was naturally cooled to room temperature in air to obtain a Fe3BO6 powder material.

[0039] like Figure 7 The figure shows the XRD pattern of the Fe3BO6 powder sample obtained in Example 2. As can be seen from the figure, the main characteristic peaks of the XRD of the obtained sample correspond to the characteristic peaks of the standard card ICDD 01-070-0880, indicating that the prepared powder material is indeed Fe3BO6.

[0040] Figure 8 This is the hysteresis loop of Fe3BO6 powder measured directly at 300 K. M - H The graph shows that the exchange bias field corresponding to the obtained Fe3BO6 is approximately 2410 Oe. Since the test process did not involve any heating or cooling of the magnetic field, this phenomenon is also a spontaneous exchange bias effect.

[0041] Although the exchange bias field size corresponding to 300 K in Example 2 is smaller than the exchange bias field size corresponding to 300 K in Example 1, the exchange bias effect is still relatively strong.

[0042] Comparative Example:

[0043] First, according to the atomic percentage of Fe3BO6, α-Fe2O3 powder with a purity of 99.5% and boric acid powder with a purity of 99.99% were weighed; the high-purity boric acid powder and α-Fe2O3 powder were then uniformly mixed; the uniformly mixed powder sample was then heated to 670°C at a heating rate of 5°C / min in an air atmosphere and kept at this temperature for 48 hours to perform a first high-temperature solid-phase reaction; the temperature was further heated to 750°C at a heating rate of 2°C / min in an air atmosphere and kept at this temperature for 24 hours to perform a second high-temperature solid-phase reaction; finally, the obtained sample was cooled to room temperature by natural cooling in the furnace to obtain the Fe3BO6 powder material sample in this comparative example.

[0044] Different from Example 1, the average particle size of the α-Fe2O3 powder used in this example is on the order of 10 μm.

[0045] like Figure 9 The XRD pattern of the Fe3BO6 powder sample obtained in this example is shown in the figure. It can be seen from the figure that the main characteristic peaks of the XRD of the obtained sample are the same as those in Example 1. Figure 1The characteristic peaks shown are different, but they all correspond to the characteristic peaks of the standard card ICDD 01-070-0880. Figure 9 The characteristic peaks shown are also consistent with the results reported in the literature (Ram S., Kumari K., Kotnala RK Synthesis of Norbergite Fe3BO6 of Single Crystallites from a Borate Glass [J]. Transactions of the Indian Ceramic Society, 2015, 69(3): 165-170), indicating that the powder material prepared in this comparative example is also Fe3BO6.

[0046] Figure 10 The hysteresis loop of the Fe3BO6 powder obtained in this comparative example was directly measured at 300 K. M - H As can be seen from the figure, the curve is well symmetric with respect to the origin, and only a very weak exchange bias effect is observed. The exchange bias field is only about 26 Oe, which is much smaller than the exchange bias field of the samples obtained in Examples 1 and 2 at 300 K.

Claims

1. A method for preparing Fe3BO6 material with strong spontaneous exchange bias effect at room temperature, characterized in that: The following steps are involved: 1) Weigh boric acid powder and nano-sized α-Fe2O3 powder according to the atomic percentage of Fe3BO6; 2) Evenly mix boric acid powder and nano-sized α-Fe2O3 powder; 3) The uniformly mixed powder sample was heated to 670°C in an air atmosphere and kept at this temperature for 48 hours to carry out the first step of high-temperature solid-phase reaction; 4) Continue heating to 750°C ~ 860°C in air atmosphere and keep warm for 24 hours to carry out the second step of high-temperature solid-phase reaction; 5) The obtained sample is naturally cooled to room temperature to obtain Fe3BO6 powder material.

2. The method for preparing a Fe3BO6 material having a strong spontaneous exchange bias effect at room temperature according to claim 1, characterized in that: In the step 1), the purity of the boric acid powder and the nano-sized α-Fe2O3 powder is controlled at 99.5% to 99.99%.

3. The method for preparing a Fe3BO6 material having a strong spontaneous exchange bias effect at room temperature according to claim 1, characterized in that: In the step 1), the average particle size of the nano-sized α-Fe2O3 powder is in the range of 30 nm to 50 nm.

4. The method for preparing a Fe3BO6 material having a strong spontaneous exchange bias effect at room temperature according to claim 1, characterized in that: In step 3), the heating rate of the first high-temperature solid-phase reaction is 5°C / min.

5. The method for preparing a Fe3BO6 material having a strong spontaneous exchange bias effect at room temperature according to claim 1, characterized in that: In step 4), the heating rate of the second high-temperature solid-phase reaction is 2°C / min.

6. The method for preparing a Fe3BO6 material having a strong spontaneous exchange bias effect at room temperature according to claim 1, characterized in that: In the step 4), the holding temperature of the second step high-temperature solid phase reaction is 750°C.

7. The method for preparing a Fe3BO6 material having a strong spontaneous exchange bias effect at room temperature according to claim 1, characterized in that: In step 5), the sample is cooled in the furnace or naturally cooled in the air.

Images