  Spin-wave resonance (SWR) is a newly emerged method for studying surface
magnetic anisotropy and surface spin-wave modes (SSWMs) in (Ga,Mn)As thin
films. The existence of SSWMs in (Ga,Mn)As thin films has recently been
reported in the literature; SSWMs have been observed in the in-plane
configuration (with variable azimuth angle $\phi_M$ between the in-plane
magnetization of the film and the surface [100] crystal axis), in the azimuth
angle range between two in-plane critical angles $\phi_{c1}$ and $\phi_{c2}$.
We show here that cubic surface anisotropy is an essential factor determining
the existence conditions of the above-mentioned SSWMs: conditions favorable for
the occurrence of surface spin-wave modes in a (Ga,Mn)As thin film in the
in-plane configuration are fulfilled for those azimuth orientations of the
magnetization of the sample that lie around the hard axes of cubic magnetic
anisotropy. This implies that a hard cubic anisotropy axis can be regarded in
(Ga,Mn)As thin films as an easy axis for surface spin pinning.
