, Volume 13, Issue 1, pp 245-255
Date: 18 Jul 2010

Morphology and magnetic properties of island-like Co and Ni films obtained by de-wetting

Abstract

The morphological, structural, and magnetic properties of Co and Ni films of different thicknesses grown by RF sputtering on a Si–SiO substrate and submitted to controlled diffusion of atoms on the substrate (de-wetting) are studied through X-ray diffraction (XRD), atomic force microscopy, X-ray photoelectron spectroscopy, and alternating-gradient magnetometry. For both metals, de-wetting treatment leads to the growth of non-percolating, metallic nanoislands characterized by a distribution of sizes and aspect ratios. XRD spectra reveal a polycrystalline multi-component structure evolving by effect of de-wetting and directly affecting the magnetic properties of films. The magnetic response after de-wetting is consistent with the formation of a nanogranular magnetic phase characterized by a complex, thickness-dependent magnetic behavior originating from the simultaneous presence of superparamagnetic and blocked-particle contributions. At intermediate film thickness (around 10 nm), a notable enhancement in magnetic coercivity is observed for both metals with respect to the values measured in precursor films and in their bulk counterparts.

S. Gupta—On leave from University of Missouri, 65211 Columbia, MO, USA.