Magnetic field effects on surface spin waves in a body-centered-cubic antiferromagnet

The effect of a magnetic field applied perpendicular to the spin-preferred axis on surface spin waves in a body-centered-cubic antiferromagnet is studied theoretically. The continuum model for the magnetic medium is adopted to study the acoustic mode of surface waves. It is found that the surface spin-wave frequency increases with increasing magnetic field and that the surface mode merges into the bulk spin-wave band if the magnetic field $H$ becomes equal to $H_c{\left[2\right(1+f\xi \left)\right]}^{\frac{1}{2}}$. Here $H_c$ denotes the spin-flop critical field, $\xi$ is the angle between the quantization axis of the surface spin and that of the bulk spin, and $f$ is a numerical factor which is smaller than unity.