Magnetic anisotropy in Ni/Fe and Fe/Cu/NiFe multilayers

Multilayer samples of Ni/Fe and Fe/Cu/NiFe, fabricated by sputtering and characterized by transmission electron microscopy and electron diffraction, were studied by 57 Fe Mössbauer spectra and magnetization measurements. Mössbauer spectra taken in zero applied field at 300 K and 4.2 K showed midlayer and interface iron sites in Ni(20 Å)/Fe( x Å) samples with x = 20 Å, 30 Å, 50 Å, 80 Å and in-plane spin orientation. The reorientation of the magnetic moments at 4.2 K in increasing fields applied normal to the layers when combined with magnetization measurements enabled the magnetic anisotropy energy K of each sample to be evaluated. The trend of the values of K with iron layer thickness gave volume and interface anisotropy components K V = (-5±1) × 10 4 J m -3 and K S = (-0.6±0.4) × 10 -3 J m -2 where negative values indicate in-plane preference. Similar measurements on a series of samples of Fe(30 Å)/Cu( x Å)/Ni(80%)Fe(20%)(30 Å) with x = 10 Å, 20 Å, 30 Å, 50 Å showed a tendency toward increasing in-plane anisotropy energy K with decreasing thickness of the non-magnetic Cu layer.