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首页> 外文期刊>Journal of Alloys and Compounds: An Interdisciplinary Journal of Materials Science and Solid-state Chemistry and Physics >Weak ferromagnetism and exchange bias effect in Co1+yAl2-yO4/SiO2 nanocomposites
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Weak ferromagnetism and exchange bias effect in Co1+yAl2-yO4/SiO2 nanocomposites

机译：Co1 + YAL2-YO4 / SiO2纳米复合材料中弱铁磁性和交换偏置效应

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摘要

Nanocomposites made of magnetic spinel oxide Co1+yAl2-yO4 nanoparticles (NPs) with y = 0.93, 1.20 and 1.34 dispersed in an amorphous SiO2 matrix were prepared by a sol-gel method. The average crystallite size D-XRD of about 25 nm determined by X-ray diffraction (XRD) agrees well with the average particle size observed in transmission electron microscopy (TEM). Dynamic magnetic susceptibility measurements indicate a spin-glass-like behavior of the nanoparticles below the spin-glass (SG) transition temperature T-C < 10 K. Field dependent magnetization exhibits weak ferromagnetism and shift of the magnetic hysteresis loop. On the basis of the observed magnetic properties, we propose a model of the core-shell structure of the Co1+yAl2-yO4 nanoparticles with the spin-glass phase in the core and weak ferromagnetism in the shell. The exchange bias field disappears above the spin-glass transition temperature TC, whereas the weak ferromagnetism persists also at temperatures above TC. The component of weak ferromagnetism is associated with the presence of Co vacancies in the nanoparticle spinel crystal lattice. (C) 2020 Elsevier B.V. All rights reserved.
机译：采用溶胶-凝胶法制备了y=0.93、1.20和1.34的磁性尖晶石氧化物Co1+yAl2-yO4纳米颗粒（NPs）在非晶态SiO2基体中的纳米复合材料。X射线衍射（XRD）测定的平均晶粒尺寸D-XRD约为25 nm，与透射电子显微镜（TEM）观察到的平均粒径一致。动态磁化率测量表明，在自旋玻璃（SG）转变温度T-C<10 K以下，纳米颗粒表现出类似自旋玻璃的行为。磁场相关磁化显示出弱铁磁性和磁滞回线的偏移。基于所观察到的磁性，我们提出了一个Co1+yAl2-yO4纳米颗粒的核-壳结构模型，核中有自旋玻璃相，壳中有弱铁磁性。在自旋玻璃化转变温度TC以上，交换偏置场消失，而在TC以上的温度下，弱铁磁性也持续存在。弱铁磁性成分与纳米颗粒尖晶石晶格中存在的Co空位有关。（C） 2020爱思唯尔B.V.版权所有。

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