Low Temperature Physics: 40, 84 (2014); https://doi.org/10.1063/1.4862465
Spin waves in an easy-axis antiferromagnet with precessing domain wall
М.М. Bogdan and О.V. Charkina
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Lenin Ave., Kharkov 61103, Ukraine
Received Octouber 25, 2013
The equations for antiferromagnetism vector are used to investigate the spectrum of spin waves and their scattering by the domain wall with the precessing spins in an easy-axis antiferromagnet at a constant magnetic field applied along the easy axis. It is shown that the magnetic field can be completely eliminated from the equations of motion whereupon they can be reduced to the Lorentz-invariant ones. The problem on a small excitation spectrum of the precessing domain wall is solved and exact solutions of the linearized equations describing the propagation of spin waves in the antiferromagnet with the domain wall are found. An explicit expression for the reflection coefficient of spin waves from the domain wall as a function of wave vectors of incident and transmitted waves, and its dependence on frequency of spin waves are obtained. A frequency range within which they are fully reflected is found and a dramatic decrease of the reflection coefficient above the upper limit of the interval is demonstrated. It is shown that the results can be generalized to the case of a moving domain wall in a three-dimensional crystal.
PACS: 75.60.Ch Domain walls and domain structure;
Key words: antiferromagnet, easy-axis anisotropy, domain wall, spin waves, excitation spectrum, reflection coefficient.