Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, University of Science and Technology of China (USTC), Hefei, People's Republic of China.
Nanotechnology. 2011 Sep 23;22(38):385701. doi: 10.1088/0957-4484/22/38/385701. Epub 2011 Aug 25.
A spin cluster glass behavior and a complicated exchange bias effect are observed in high quality BiFeO(3) nanocrystals grown by a hydrothermal method. The dynamic properties of the spin clusters investigated by measuring the frequency dependences of ac susceptibility show that the relaxation process can be described using a power law with the glass transition temperature T(g) = 57 K, relaxation time constant τ(0) = 4.4 × 10(-10) s, and critical exponent zv = 10.3 ± 1.9, consistent with a three-dimensional Ising spin glass. The exchange bias field (H(EB)) varies non-monotonically with temperature and achieves a minimum at T(g). The abnormal shift of hysteresis loops above T(g) may be interpreted in terms of a Malozemoff's random-field model with a framework of antiferromagnetic core/spin-cluster shell structure and a two-dimensional diluted antiferromagnet in a field (2D-DAFF) model, respectively. The exchange anisotropy of the BiFeO(3) nanocrystals will shed light on a possible application for magnetism related nanosized devices.
在水热法生长的高质量 BiFeO(3) 纳米晶体中观察到自旋团簇玻璃行为和复杂的交换偏置效应。通过测量交流磁化率的频率依赖性研究自旋团簇的动态特性表明，弛豫过程可以用幂律描述，玻璃化转变温度 T(g) = 57 K，弛豫时间常数 τ(0) = 4.4 × 10(-10) s，临界指数 zv = 10.3 ± 1.9，与三维 Ising 自旋玻璃一致。交换偏置场 (H(EB)) 随温度非单调变化，并在 T(g) 处达到最小值。在 T(g) 以上，磁滞回线的异常偏移可以分别用 Malozemoff 随机场模型和具有反铁磁核/自旋团簇壳结构和场中的二维稀释反铁磁体 (2D-DAFF) 模型来解释。BiFeO(3) 纳米晶体的交换各向异性将为与磁性相关的纳米器件的应用提供启示。
