Title :
Soft magnetic properties and heat stability for Fe/NiFe superlattices
Author :
Motomura, Y. ; Tatsumi, T. ; Urai, H. ; Aoyama, M.
Author_Institution :
NEC Corp., Kanagawa, Japan
fDate :
9/1/1990 12:00:00 AM
Abstract :
Soft magnetic properties and heat stability were investigated for Fe/NiFe (91 wt.% Ni and 19 wt.% Fe) superlattice films. 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 (H c) value and relative permeability (μ) depend on the thicknesses of both Fe and NiFe layers. Saturation magnetostriction constant (λs) behavior is explained as the average of λs values for Fe, NiFe, and Fe-NiFe interdiffusion layers. In Fe/NiFe films with 8~16-nm, superlattice modulation wavelength and around 50% Fe-layer thickness ratio, large 15-kG 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 values are 1.9×10-24 ~1.5×10-21 m2 s-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 effective interdiffusivity value to lower temperature, Fe/NiFe films appear rather stable at an operating temperature for hard disk drives
Keywords :
X-ray diffraction examination of materials; coercive force; ferromagnetic properties of substances; iron; iron alloys; magnetic permeability; magnetic thin films; magnetostriction; metallic superlattices; nickel alloys; Arrhenius temperature dependence; Fe-NiFe; X-ray diffraction; effective interdiffusivity value; hard disk drives; heat stability; interdiffusivity values; magnetic flux density; magnetostriction constant; relative permeability; soft magnetic properties; superlattice modulation wavelength; superlattice periodicity; FCC; Iron; Magnetic films; Magnetic flux density; Magnetic properties; Magnetic superlattices; Stability; Stacking; Temperature dependence; X-ray diffraction;
Journal_Title :
Magnetics, IEEE Transactions on
