Transition Temperature of Wurtzite CoO Nanocrystals as Revealed in Comprehensive Magnetic Characterization

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• 作者：Xuemin He ; Wei Zhong ; Shiming Yan ; Chao Liu ; Huigang Shi ; Chak-Tong Au ; Youwei Du
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：June 26, 2014
• 年：2014
• 卷：118
• 期：25
• 页码：13898-13903
• 全文大小：372K
• ISSN：1932-7455

文摘

We conducted magnetic study over wurtzite CoO nanocrystals (about 45 nm in size). The blocking temperature T_B and N茅el temperature T_N were confirmed by comprehensive magnetic characterization. Below T_B of 7 K the nanocrystals exhibit coercivity of 400 Oe and exchange bias of 206 Oe ascribable to composition influences of uncompensated surface spins as well as to antiferromagnetic volume phase. The uncompensated magnetic sublattice and the spatial distribution of the anisotropy axis relative to the magnetic field are proposed to be responsible for the distinct electron spin resonance (ESR) line shape. Based on the temperature dependence of ESR intensity, the accurate T_N is found to be 245 K. It is observed that there is anomalous change in resonance field and line width around T_N.