Spin-torque-biased magnetic dynamics in an easy-plane ferromagnet (EPF) is theoretically studied in the presence of a weak in-plane anisotropy. While this anisotropy spoils U(1) symmetry thereby quenching the conventional spin superfluidity, we show that the system instead realizes a close analog of a long Josephson junction (LJJ) model. The traditional magnetic-field and electric-current controls of the latter map respectively onto the symmetric and antisymmetric combinations of the out-of-plane spin torques applied at the ends of the magnetic strip. This suggests an alternative route towards realizations of superfluid-like transport phenomena in insulating magnetic systems. We study spin-torque-biased phase diagram, providing analytical solution for static multidomain phases in the EPF. We adapt an existing self-consistency method for the LJJ to develop an approximate solution for the EPF dynamics. The LJJ-EPF mapping has potential for producing applications with superconductor-based circuit functionality at elevated temperatures. The results apply equally to antiferromagnets with suitable effective free energy in terms of the N\'{e}el order instead of magnetization.

中文翻译：

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自旋扭矩偏置磁条：非平衡相图和与长约瑟夫森结的关系

理论上在存在弱平面内各向异性的情况下，对易平面铁磁体（EPF）中的自旋转矩偏置的磁动力学进行了研究。虽然此各向异性破坏了U（1）的对称性，从而消除了常规的自旋超流动性，但我们表明，该系统实际上实现了长约瑟夫森结（LJJ）模型的近似模拟。后者的传统磁场和电流控制分别映射到施加在磁条末端的平面外旋转转矩的对称和反对称组合。这提出了在绝缘磁系统中实现超流体类传输现象的另一种方法。我们研究了自旋转矩偏置相图，为EPF中的静态多域相提供了解析解决方案。我们为LJJ调整了现有的自洽方法，为EPF动力学开发了一种近似解决方案。LJJ-EPF映射具有在高温下生产具有基于超导体的电路功能的应用的潜力。该结果同样适用于具有合适的有效自由能的反铁磁体，这些反自由磁体的磁阶为N \'{e} el而不是磁化。