Pinning, rotation, and metastability of BiFeO 3 cycloidal domains in a magnetic field
Pinning, rotation, and metastability of BiFeO 3 cycloidal domains in a magnetic field
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BiFeO 3 摆线磁畴在磁场中的钉扎、旋转和亚稳态
DOI：
10.1103/physrevb.97.014405
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发表时间：
2017
影响因子：
3.7
通讯作者：
R. Fishman
中科院分区：
文献类型：
--
作者：
R. Fishman
早期的室温多铁性BiFeO3模型隐含地假设了很强的各向异性将域波矢量q限制在与静态极化p垂直的三重对称轴上。最近的测量表明，域波矢量旋转，使q在远离场方向m的法向P的六角形平面内旋转。我们表明，以前被忽视的三向各向异性K3限制了波矢量在零场中沿三向轴旋转。对于沿三重轴的m， q平行于m的畴在Bc1 = 7 T以下保持亚稳，由于非磁性杂质对畴的固定，当转矩沿P的分量T = m x B超过阈值tpin时，其他两个畴的波向量在5.6 T以上开始远离m旋转。因为当m垂直于q时，t =0，这些区域的波矢量永远不会完全垂直于磁场。我们的结果解释了最近的关键场测量作为场方向的函数，波矢量的小角度中子散射测量，以及沿着三重轴的m光谱测量。
Earlier models for the room-temperature multiferroic BiFeO3 implicitly assumed that a very strong anisotropy restricts the domain wavevectors q to the three-fold symmetric axis normal to the static polarization P. However, recent measurements demonstrate that the domain wavevectors rotate so that q rotates within the hexagonal plane normal to P away from the field orientation m. We show that the previously neglected three-fold anisotropy K3 restricts the wavevectors to lie along the three-fold axis in zero field. For m along a three-fold axis, the domain with q parallel to m remains metastable below Bc1 = 7 T. Due to the pinning of domains by non-magnetic impurities, the wavevectors of the other two domains start to rotate away from m above 5.6 T, when the component of the torque t = M x B along P exceeds a threshold value tpin. Since t =0 when m is perpendicular to q, the wavevectors of those domains never become completely perpendicular to the magnetic field. Our results explain recent measurements of the critical field as a function of field orientation, small-angle neutron scattering measurements of the wavevectors, as well as spectroscopic measurements with m along a three-fold axis.