Interdependence of magnetic properties and intrinsic stress in mono- and polycrystalline thin nickel films

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Abstract
Mono- and polycrystalline Ni films, ranging in thickness from 19 to 382 nm, have been produced by vacuum deposition on (001) monocrystalline Ag/NaCl and on glass substrates, respectively. Subsequently, saturation magnetization Ms, magnetogyric factor γ/2π, and effective uniaxial anisotropy Hk were measured by a combination of vibrating sample magnetometer and ferromagnetic resonance (FMR), and corresponding internal stress σ was measured by a levered optical beam reflection technique. In addition, the microstructure of both mono- and polycrystalline films has been characterized by conventional and cross-section transmission electron microscopy. Saturation magnetization can be interpreted by the presence of a magnetic dead layer of about 9 nm and a constant value of 434 emu/cm3, thereafter. Results from FMR can be described by contributions from shape and stress-induced anisotropy. Corresponding values of σ, as computed from Hk, are in satisfactory agreement with values measured by the optical beam reflection technique and yield values of about 1010 dyn/cm2; σ generally decreases with increasing film thickness and annealing time and temperature. Finally, monocrystalline films are characterized by a single FMR peak; polycrystalline films thicker than about 200 nm are characterized by multiple peaks. Occurrence of these multiple peaks is attributed to variation in the effective magnetoelastic constant as a result of a change from equiaxed to columnar grain morphology.

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