Modelling the magnetorefractive effect in giant magnetoresistive granular and layered materials

The Zhang–Levy–Granovskii (Z–L–G) model of the magnetorefractive effect (MRE) in granular films and the Jacquet–Valet (J–V) model, originally developed for magnetic multilayers, are compared and their common origin demonstrated. Simulations in an extended Hagen–Rubens (H–R) model give new insight into the variation with wavelength of the MRE, and the relative dependence of giant magnetoresistance (GMR) and the MRE to material and experimental parameters such as bulk and interface scattering parameters, mean free paths, grain diameter, polarisation and reflection geometry is explored. The sensitivity of the size, wavelength dependence and the position of the depth of the minimum in the MRE spectra to the different parameters is verified. We establish powerful new equations to correlate the MRE and GMR, and we analyse their validity for a variety of film parameters. This suggests a new approach to the use of the MRE in sensing GMR in the films.     

About the depth sensitivity of second-harmonic radiation in ultra-thin metal films

Second-harmonic generation (SHG) results for Ni and Co films on Cu (001) have been reinvestigated regarding the depth sensitivity of this technique for thin films. We find that tangential components of the nonlinear susceptibility are much more sensitive to real film properties than normal components, which are confined to surfaces and interfaces. In consequence, for SHG experiments on ultra-thin metal films, polarization combinations should be favored that possess only tangential susceptibility components, even though the yield is weaker. Additional phase measurements are necessary to obtain full information about the film. Received: 20 January 2002 / Published online: 6 June 2002     

Influence of sputtering pressure on the giant magnetoresistance and structure in Fe–Cu–Ni granular thin films

Composition, structure and giant magnetoresistance in Fe_xCu_yNi_z films prepared at different sputtering pressures were investigated. X-ray diffraction studies showed only Cu (1 1 1) peak from the Cu grain. The shifts in the d-spacing d₁₁₁ of Cu indicates a progressive substitution of Ni in the Cu lattice. Similar trends in d₁₁₁ of Cu observed for the samples prepared at different sputtering pressures indicate that the structural behaviour of the samples is nearly independent of the sputtering pressure. A significant enhancement of magnetoresistance (MR) for the samples sputtered at 0.001 mbar as compared to that sputtered at 0.02 mbar is attributed to the reduced role of residual gas impurities in the films upon lowering the sputtering pressure. An interesting observation is that the MR did not significantly decrease even with a large substitution of Ni in the Cu grains.