Local stiffness and stability of the ferromagnetic state in metals

The concept of local stiffness associated with transverse local spin fluctu ations is introduced and used to investigate the coupling between the magne tization of atomic planes in the ferromagnetic state of a metallic material . It is shown that the coupling strength in the surface region may differ s ignificantly from that in the bulk, and the possibility of an antiferromagn etic alignment between surface and bulk magnetizations is pointed out. A co mparison between calculated values of local and spin-wave stiffnesses is pr esented, and the stability of the ferromagnetic state against both short- a nd long-wavelength spin fluctuations is discussed.