STATIC MAGNETIZATION DIRECTION UNDER PERPENDICULAR SURFACE ANISOTROPY

The problem of depth dependence of the magnetization tilt angle (z) is solved analytically for an exchange-coupled ferromagnet with dipole energy, applied field, and surface anisotropy Ks. For Ks (M2A)1/2=Kc, the surface magnetization direction remains in the plane, s=(0)=/2. For Ks Kc, the magnetization vector moves out of the surface, initially with d s/dKs=-, then slowly approaches s=0 as Ks approaches infinity. For Fe, Kc is of order 4 erg/cm2. The results indicate that a perpendicular component of magnetization at the surface relaxes to its bulk in-plane orientation over a distance that is generally much shorter than the bulk domain-wall width. The surface remanence and initial susceptibility of the surface magnetization for in-plane applied field are calculated and provide useful expressions for interpreting experimental results. The experimentally measured surface magnetization increases linearly with probe sensitivity depth. © 1990 The American Physical Society.