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arXiv · 1802.04229

Easy-Plane Magnetic Strip as a Long Josephson Junction

Daniel Hill·Se Kwon Kim·Yaroslav Tserkovnyak
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Abstract

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 an 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 allows us to envision superconducting 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.

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Daniel Hill, Se Kwon Kim, Yaroslav Tserkovnyak. 2018-02-12. Easy-Plane Magnetic Strip as a Long Josephson Junction. https://doi.org/10.1103/physrevlett.121.037202

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