THE CORRELATION OF LOCAL STRUCTURE AND MAGNETISM IN THIN FERROMAGNETIC FILMS

Abstract

The most important quantity in magnetism is the magnetic anisotropy energy (MAE). Small MAE corresponds to soft magnets, good for transformers; large MAE corresponds to hard magnets, good for storage media. On a surface and nanometer scale LEED, MEED, X-ray and photoelectron diffraction, surface EXAFS and other techniques have recently made enormous progress in the determination of the real nearest neighbor distances and interlayer spacings within a tenth of an angstrom. These parameters serve as input for ab initio calculations of the MAE. Recent experiments on ultrathin Ni and Co films on Cu and W substrates will be discussed. We show that small displacements from ideal the fcc structure by only 2% may change the MAE by orders of magnitude! Thus for the first time the origin of the MAE in thin films can be understood on the basis of first-principles calculations taking into account the real local, i.e. noncubic perturbed, structure. This will result in an intimate contact between surface structure determination and magnetic properties.