Spin-flop transition in uniaxial antiferromagnets:: Magnetic phases, reorientation effects, and multidomain states
Spin-flop transition in uniaxial antiferromagnets:: Magnetic phases, reorientation effects, and multidomain states
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DOI：
10.1103/physrevb.75.094425
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发表时间：
2007-03-01
影响因子：
3.7
通讯作者：
Roessler, U. K.
中科院分区：
文献类型：
--
作者：
Bogdanov, A. N.;Zhuravlev, A. V.;Roessler, U. K.
经典的自旋翻转是场驱动的易轴反铁磁体的一级重取向跃迁。发展了易轴反铁磁体自旋翻转的唯象理论。它示出了如何在这些反铁磁体的磁耦合强度的层次结构导致一个强烈的显着的两个尺度的字符在其磁相结构。与磁相图的主要部分相反，自旋翻转区附近的反铁磁体由类似于单轴铁磁体的有效模型描述。对于一个一致的理论描述高阶各向异性的贡献和偶极杂散场必须考虑到附近的自旋翻转。特别是，在自旋触发器区域中，由于在这个一阶转变处的相共存，存在着双稳态的多畴态。对于这个区域，多畴态的平衡自旋组态和参数导出作为外磁场的函数。磁化率张量的分量计算的均匀和多畴状态附近的自旋翻转。在这些可测量的量的可观的异常提供了一个有效的方法来调查磁状态，并确定在散装和限制反铁磁体，以及在纳米合成反铁磁体的材料参数。该方法被证明为正交层状反铁磁体（C2H5NH3）（2）CuCl 4的自旋翻转区附近的磁性的实验数据。
The classical spin flop is the field-driven first-order reorientation transition in easy-axis antiferromagnets. A comprehensive phenomenological theory of easy-axis antiferromagnets displaying spin flops is developed. It is shown how the hierarchy of magnetic coupling strengths in these antiferromagnets causes a strongly pronounced two-scale character in their magnetic phase structure. In contrast to the major part of the magnetic phase diagram, these antiferromagnets near the spin-flop region are described by an effective model akin to uniaxial ferromagnets. For a consistent theoretical description both higher-order anisotropy contributions and dipolar stray fields have to be taken into account near the spin flop. In particular, thermodynamically stable multidomain states exist in the spin-flop region, owing to the phase coexistence at this first-order transition. For this region, equilibrium spin configurations and parameters of the multidomain states are derived as functions of the external magnetic field. The components of the magnetic susceptibility tensor are calculated for homogeneous and multidomain states in the vicinity of the spin flop. The appreciable anomalies in these measurable quantities provide an efficient method to investigate magnetic states and to determine materials parameters in bulk and confined antiferromagnets, as well as in nanoscale synthetic antiferromagnets. The method is demonstrated for experimental data on the magnetic properties near the spin-flop region in the orthorhombic layered antiferromagnet (C2H5NH3)(2)CuCl4.