title: Dynamic properties of spin cluster glass and the exchange bias effect in BiFeO3 nanocrystals.
abstract: 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.
authors.affiliation: 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.
authors.forename: Sining
authors.initials: S
authors.lastname: Dong
authors.forename: Yiping
authors.initials: Y
authors.lastname: Yao
authors.forename: Ying
authors.initials: Y
authors.lastname: Hou
authors.forename: Yukuai
authors.initials: Y
authors.lastname: Liu
authors.forename: Yang
authors.initials: Y
authors.lastname: Tang
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Li