Observation of the exchange interaction at the surface of a ferromagnet

The temperature dependence of the surface magnetization MS(T) in the spin-wave regime is obtained from measurement of the spin polarization of the low-energy cascade electrons. With the T32 law, the ratio k of the mean spin deviation in surface and bulk is determined, where k reflects the perpendicular exchange interaction. In the ferromagnetic glass FeNiB0.5, depends critically on the chemistry of the first layer and is weakened even with a bulklike surface composition. © 1988 The American Physical Society.