MICROSTRUCTURE AND MAGNETOELASTIC COUPLING-COEFFICIENTS IN THIN NIFE AND NI FILMS

The effective magnetoelastic (ME) coupling coefficients B-eff of polyc rystalline Ni79Fe21 and Ni films have been reported as functions of th ickness t. B-eff was observed to have a thickness-independent bulk ter m, B-b, and a thickness-dependent surface term, B-s/t consistent with the Neel model. For thickness below 50 Angstrom the surface term is im portant; it can change the sign of the effective ME coupling constant and dramatically increase its magnitude. We expect that the surface ME coupling we observe in polycrystalline thin films may be a combinatio n of the intrinsic Neel surface effect and extrinsic microstructure ef fects. Our transmission electron microscopy, Auger depth profiling, an d atomic force microscopy rule out film discontinuity and compositiona l gradients as significant sources of he surface ME effect. (C) 1996 A merican Institute of Physics.