Thermal fluctuation and magnetization of Ni-Zn ferrite nanoparticles by particle size
Thermal fluctuation and magnetization of Ni-Zn ferrite nanoparticles by particle size
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DOI：
10.1007/s10973-005-0819-y
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发表时间：
2005-08
影响因子：
4.4
通讯作者：
Y. Ichiyanagi;Tetsuya Uehashi;Saori Yamada;Y. Kanazawa;Tsutomu Yamada
中科院分区：
文献类型：
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作者：
Y. Ichiyanagi;Tetsuya Uehashi;Saori Yamada;Y. Kanazawa;Tsutomu Yamada
采用湿化学法制备了非晶SiO2包裹的Ni1-xZnxFe2O4(0≤x≤1)混合铁氧体纳米粒子。通过热处理将粒径控制在2.6至33.7 nm范围内，并在x=0.5区域研究了饱和磁化强度Ms的粒径依赖性。当粒径低于约 6 nm 时，Ms 值突然下降。根据场冷却和零场冷却条件下磁化强度的温度依赖性，观察到阻塞温度 Tb 在 28 到 245 K 之间，具体取决于颗粒尺寸。在阻挡温度下，粒子中的超顺磁自旋应该被热波动能量阻挡。颗粒体积越小，阻塞温度越低；因此，极小的粒子会受到热波动的强烈影响。
Ni1-xZnxFe2O4(0≤x≤1) mixed ferrite nanoparticles encapsulated with amorphous-SiO2were prepared by a wet chemical method. Particle sizes were controlled to range from 2.6 to 33.7 nm by heat treatment, and the particle size dependence of saturation magnetization Mswas investigated for thex=0.5 region. The Msvalue decreased abruptly for particle sizes below about 6 nm. From the temperature dependence of the magnetization under field-cooled and zero-field-cooled conditions, blocking temperatures Tbwere observed to be between 28 and 245 K depending on the particle size. At the blocking temperature, the superparamagnetic spins in the particle are supposed to be blocked against the thermal fluctuation energy. A smaller particle volume causes a lower blocking temperature; so an extremely small particle would be strongly affected by thermal fluctuation.