Microstructure and magnetic characteristics of nanocrystalline Ni0.5Zn0.5 ferrite synthesized by a spraying--coprecipitation method
Liu Yin(刘银)a) b) † and Qiu Tai(丘泰)a)
a College of Materials Science and Engineering, Nanjing University of Technology, Nanjing 210009, China; b Department of Materials Science and Engineering, Anhui University of Science and Technology, Huainan 232001, China
Abstract Nanocrystalline Ni$_{0.5}$Zn$_{0.5}$ ferrite with average grain sizes ranging from 10 to 100~nm is prepared by using a spraying--coprecipitation method. The results indicate that the nanocrystalline Ni$_{0.5}$Zn$_{0.5}$ ferrite is ferromagnetic without the superparamagnetic phenomenon observed at room temperature. Specific saturation magnetization of nanocrystalline Ni$_{0.5}$Zn$_{0.5}$ ferrite increases from 40.2 to 75.6 emu/g as grain size increases from 11 to 94nm. Coercivity of nanocrystalline Ni$_{0.5}$Zn$_{0.5}$ ferrite increases monotonically when $d < 62$ nm.The relationship between the coercivity and the mean grain size is well fitted into a relation $H_{\rm c }\sim d^{3}$. A theoretically evaluated value of the critical grain size is 141nm larger than the experimental value 62nm for nanocrystalline Ni$_{0.5}$Zn$_{0.5}$ ferrite. The magnetic behaviour of nanocrystalline Ni$_{0.5}$Zn$_{0.5}$ ferrite may be explained by using the random anisotropy theory.
Accepted manuscript online:
PACS:
61.46.Df
(Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots))
(Magnetization curves, hysteresis, Barkhausen and related effects)
Fund: Project supported by the National Defence Foundation of China.
Cite this article:
Liu Yin(刘银) and Qiu Tai(丘泰) Microstructure and magnetic characteristics of nanocrystalline Ni0.5Zn0.5 ferrite synthesized by a spraying--coprecipitation method 2007 Chinese Physics 16 3837
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