SOFT MAGNETIC-PROPERTIES AND HEAT-STABILITY FOR FE-NIFE SUPERLATTICES

Soft magnetic properties and heat stability for Fe/NiFe (81wt.% Ni and 19wt.% Fe) superlattice films have been investigated. X-ray diffraction data show that the films have a textured bcc Fe (110)/fcc NiFe (111) stacking. Saturation magnetic flux density (Bs) is the average of bulk Fe and NiFe values. Coercive field (Hc) value and relative permeability (μ) depend on the thicknesses of both Fe and NiFe layers. Saturation magnetostriction constant (μs) behavior is explained as the average of λs values for Fe, NiFe and Fe-NiFe interdiffusion layers. In Fe/NiFe films with 8~16nm superlattice modulation wave length and around 50% Fe layer thickness ratio, large 15 kGauss Bs value, 3000 μ values and very small λs values less than 5×10-7 were achieved. The soft magnetic properties and the superlattice periodicity are stable at up to 200°C annealing temperature. Effective interdiffusivity (DË„) values are 1.9×10-24 ~1.5×10-21m2sec-1 in the 200 ~400°C temperature range, and are found to have an Arrhenius temperature dependence. Activation energy for the interdiffusion is estimated to be 0.84 eV. Extrapolating the DË„ value to lower temperature, Fe/NiFe films appear rather stable at an operating temperature for hard disk drives. © 1990 IEEE