CN112374877B - 具有磁阻转换行为的CoFe2O4-CrO2复合材料的制备方法 - Google Patents

具有磁阻转换行为的CoFe2O4-CrO2复合材料的制备方法 Download PDF

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CN112374877B
CN112374877B CN202011070982.3A CN202011070982A CN112374877B CN 112374877 B CN112374877 B CN 112374877B CN 202011070982 A CN202011070982 A CN 202011070982A CN 112374877 B CN112374877 B CN 112374877B
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王金凤
李亚芳
尹士莹
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Abstract

本发明公开了一种具有磁阻转换行为的CoFe2O4‑CrO2复合材料的备方法，首先在特定条件下制备出CoFe2O4‑CrO2混合粉末，将其在7MPa下压制成圆形薄片得到目标复合材料。本发明制得的复合材料不仅比纯CrO2拥有更大的矫顽场，而且还能产生磁阻转换行为。本发明在此类领域的研究中有一定突破作用，有助于探索磁阻转换行为的微观物理原理，并且本发明操作简单易制备且重复性高。

Description

具有磁阻转换行为的CoFe2O4-CrO2复合材料的制备方法
技术领域
本发明属于磁阻复合材料技术领域，具体涉及一种具有磁阻转换行为的CoFe2O4-CrO2复合材料的制备方法。
背景技术
隧穿磁电阻(TMR)效应是指在铁磁层/非磁绝缘层/铁磁层这样的磁性隧道结中，当外加磁场使两铁磁层的磁化方向由平行态向反平行态转变的过程中，两层间的电阻值会发生从低电阻态向高电阻态转变的现象。这个效应在磁性测量曲线上表现为，当外加磁场由负磁场向正磁场变化时HC(MR)为正值，反向变化时HC(MR)为负值，且HC(MR)=HC，其中HC(MR)对应电阻最大时的磁场，HC是矫顽场。 M.Julliere从Fe/Ge/Co隧道结中首先发现了TMR效应(Julliere M.Tunneling between ferromagnetic flims. Phys. Lett. A.1975, 54:225-226)。后来人们利用TMR的这种性质，将这种材料广泛应用在硬盘的读出磁头和各类传感器上。
随后人们在研究多层薄膜材料时发现了自旋阀式磁阻效应(SVMR)。这个效应与TMR类似，但不同的是，在这个效应中HC(MR)
Figure DEST_PATH_IMAGE002
HC(Dieny B., Speriosu V. S., Parkin S.S. P., et al. Gaint magnetoresistance in soft ferromagnetic multilayers.Phys. Rev. B. 1991, 43: 1297-1300)。通过对SVMR效应的深入探索，人们发现这种效应也存在于多晶体Sr2FeMoO6材料和其它种复合材料中(Sarma D. D., Ray Sugata, TanakaK.,et al. Intergranular Magnetoresistancee in Sr2FeMoO6 from a Magnetic TunnelBarrier Mechanism across Grain Boundaries. Phys.Rev.Lett.2007,98:157205)，并且目前它已经成为制作自旋电子器件的首选依据。
在近几年的研究中研究者又发现了一种新型的磁阻转换行为，这种行为在磁性测量曲线上表现为，当外加磁场由负磁场扫向正磁场时HC(MR)为负值，反向变化时HC(MR)为正值，这不同于TMR效应和SVMR效应。并且在目前的研究工作中很少发现这种现象，只有在La2/3Sr1/3MnO3或La0.67Ca0.33MnO3钙钛矿型软磁材料与CoFe2O4硬磁材料混合的这两个体系中发现(Kumar P. Anil and Sarma D. D. Effect of “dipolar-biasing” on thetenability of tunneling magnetoresistance in transition metal oxide systems.Appl. Phys. Lett. 2012.100:262407;Muscas G., Kumar P.Anil. Barucca G.,ConcasG.,Varvaro G.,et al.Designing new ferrite/manganite nanocomposites.Nanoscale. 2016, 8: 2081-2089)。所以说这是一种全新的磁阻行为，并且这种行为的产生机理值得我们去深入探究，以便日后开发它的潜在应用价值。
本发明在一定条件下将CoFe2O4和纳米CrO2粉末混合，然后将得到的复合材料压制成薄片。随后对薄片样品进行XRD、R-H和M-H连续测试，经过数据分析，最终在这个复合材料中观察到磁阻转换行为。本发明在此类研究中有一定的突破作用，有助于探索磁阻转换行为的微观物理原理，并且本发明操作简单易制备且重复性高。
发明内容
本发明解决的技术问题是提供了一种工艺简单且成本低廉的具有磁阻转换行为的CoFe2O4-CrO2复合材料的制备方法。
本发明为解决上述技术问题采用如下技术方案，具有磁阻转换行为的CoFe2O4-CrO2复合材料的制备方法，其特征在于具体步骤为：
步骤S1：称取纯度为99.5%的纳米CoFe2O4粉末，将其置于坩埚中并在马弗炉中加热到900℃烧结6h，随炉冷却至室温；
步骤S2：将步骤S1中的粉末倒入玛瑙研钵中，再次研磨便得到所需的原料CoFe2O4；
步骤S3：按照CoFe2O4和纳米CrO2粉末理论摩尔比为1:1的比例分别计算步骤S2得到的原料CoFe2O4和纯度为99%的纳米CrO2的质量；
步骤S4：按照S3的计算结果分别称取S2中的CoFe2O4和纯度为99%的纳米CrO2原料；
步骤S5：将步骤S4称好的两种原料在玛瑙研钵中混合研磨2h，从中取出0.2g已磨好的混合粉末加压至7MPa，保压后得到直径10mm*厚度1mm的圆形薄片即为具有磁阻转换行为的CoFe2O4-CrO2复合材料。
本发明的优点在于：本发明整个实验制备过程不复杂，只需使用传统的固相烧结法，再经过粉末压制成型技术，就可以轻松获得性能良好且具有新型磁阻转换行为的CoFe2O4-CrO2复合材料。
附图说明
图1是实施例合成的CoFe2O4-CrO2复合材料的XRD图谱。
图2是纯CrO2粉末与实施例合成的复合材料分别在10K、50K、200K、300K条件下测得的M-H曲线，在图中分别由空方框线和实三角线表现，图中的HC(1)与HC(2)分别为两者的矫顽场。
图3是纯CrO2粉末(a-c)与实施例合成的复合材料(d-f)分别在10K、50K、200K时的MR%-H曲线。
具体实施方式
以下通过实施例对本发明的上述内容做进一步详细说明，但不应该将此理解为本发明上述主题的范围仅限于以下的实施例，凡基于本发明上述内容实现的技术均属于本发明的范围。
实施例
步骤S1：称取适量纯度为99.5%的纳米CoFe2O4粉末，将其置于坩埚中并在马弗炉中加热到900℃烧结6h，随炉冷却至室温；
步骤S2：将步骤S1中的粉末倒入玛瑙研钵中，再次研磨便得到实验所需的原料CoFe2O4；
步骤S3：按照CoFe2O4和纳米CrO2粉末理论摩尔比为1:1的比例分别计算步骤S2原料CoFe2O4和纯度为99%的纳米CrO2的质量；
步骤S4：按照S3的计算结果分别称取S2中的CoFe2O4和纯度为99%的纳米CrO2原料；
步骤S5：将步骤S4称好的两种原料在玛瑙研钵中混合研磨2h，从中取出0.2g已磨好的混合粉末加压至7MPa，保压后得到一个圆形薄片即为CoFe2O4-CrO2复合材料，该圆形薄片的规格约为直径10mm*厚度1mm。
测试结果：
图1是实施例的CoFe2O4-CrO2复合材料的XRD图谱。由图中可以看到，此复合材料的图谱是由CoFe2O4和CrO2两套衍射峰叠加而成。
图2是纯CrO2粉末与CoFe2O4-CrO2复合材料的M-H测试结果。这两种样品分别在10K、50K、200K和300K下进行测试，其中空方框线代表纯CrO2的测试曲线，实三角线代表CoFe2O4-CrO2复合材料的测试曲线。从10K图中可以看到在CrO2中加入CoFe2O4后，矫顽场由原来HC(1)=985Oe增大到了HC(2)=4826Oe，同样在50K、200K和300K中也观察到类似的现象。这说明了加入CoFe2O4可以提高CrO2的矫顽场。并且还有另外一个现象，对于纯CrO2或者CoFe2O4-CrO2复合材料，它们的矫顽场都会随着测试温度的降低而增大。例如，当测试温度由300K降低到10K时，CoFe2O4-CrO2复合材料的矫顽场由811Oe增大到4826Oe。
图3是纯CrO2(a-c)与CoFe2O4-CrO2(d-f)在10K、50K和200K下的MR%-H图。图中曲线左右两侧的箭头代表磁场的方向，每幅图中的插图为顶部局部放大图。由上下图形作对比可以发现对于纯CrO2在磁场由负向正变化时，其电阻最大值对应的磁场为正值，而对于CoFe2O4-CrO2复合材料，磁场由负向正变化，其电阻最大值对应的磁场为负值，这一现象就是磁阻转换行为。在以上三个温度中，这种现象均存在。并且还能从图中发现，随着温度的降低，这种磁阻转换行为更加明显。在图中表现为温度从200K降低到10K，其相对应的HC(MR)从66Oe增大到500Oe。
以上实施例描述了本发明的基本原理、主要特征及优点，本行业的技术人员应该了解，本发明不受上述实施例的限制，上述实施例和说明书中描述的只是说明本发明的原理，在不脱离本发明原理的范围下，本发明还会有各种变化和改进，这些变化和改进均落入本发明保护的范围内。

Claims (1)

1.具有磁阻转换行为的CoFe2O4-CrO2复合材料的制备方法，其特征在于具体步骤为：
步骤S1：称取纯度为99.5%的纳米CoFe2O4粉末，将其置于坩埚中并在马弗炉中加热到900℃烧结6h，随炉冷却至室温；
步骤S2：将步骤S1中的粉末倒入玛瑙研钵中，再次研磨便得到所需的原料CoFe2O4；
步骤S3：按照CoFe2O4和纳米CrO2粉末理论摩尔比为1:1的比例分别计算步骤S2得到的原料CoFe2O4和纯度为99%的纳米CrO2的质量；
步骤S4：按照S3的计算结果分别称取S2中的CoFe2O4和纯度为99%的纳米CrO2原料；
步骤S5：将步骤S4称好的两种原料在玛瑙研钵中混合研磨2h，从中取出0.2g已磨好的混合粉末加压至7MPa，保压后得到直径10mm*厚度1mm的圆形薄片即为具有磁阻转换行为的CoFe2O4-CrO2复合材料。
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CN102320660A (zh) * 2011-05-27 2012-01-18 吉林大学 二氧化铬和二氧化钛复合氧化物的高温高压制备方法
CN109279888A (zh) * 2018-10-22 2019-01-29 河南师范大学 一种自旋阀型磁阻复合材料CoFe2O4-Fe3O4的简易合成方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1441183A (en) * 1973-03-05 1976-06-30 Tdk Electronics Co Ltd Magnetic recording particles
US4244932A (en) * 1978-07-21 1981-01-13 Montedison S.P.A. Stabilized ferromagnetic chromium dioxide and process for obtaining same
US5962905A (en) * 1996-09-17 1999-10-05 Kabushiki Kaisha Toshiba Magnetoresistive element
CN1433021A (zh) * 2002-01-16 2003-07-30 株式会社东芝 磁存储器
CN101573753A (zh) * 2006-09-29 2009-11-04 日本钨合金株式会社 磁头用基板材料及其制造方法
CN102320660A (zh) * 2011-05-27 2012-01-18 吉林大学 二氧化铬和二氧化钛复合氧化物的高温高压制备方法
CN109279888A (zh) * 2018-10-22 2019-01-29 河南师范大学 一种自旋阀型磁阻复合材料CoFe2O4-Fe3O4的简易合成方法

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