Influence of film thickness on the electrical and magnetic properties of Co-Fe-Al-O films

Influence of film thickness (t) on the electrical and magnetic properties of Co-Fe-Al-O films has been systematically investigated via means of vibrating sample magnetometry (VSM), permeability spectra and magneto-optical Kerr effect (MOKE). It is found that the electrical resistivity (p) decreases as the film thickness increases; p = 412.5 mu Omega cm for the t = 600 nm sample decreases to p = 368.2 mu Omega cm for the t = 1200 nm sample. The coercive force, measured along the easy-axis direction, decreases as the film thickness increases. Interestingly, along the hard-axis magnetization direction, the magnetic hysteresis loop is reversed and the coercive force is negative for the t = 600 and 800 nm samples. However, this peculiar feature disappears as t reaches 1200 run, which is probably attributed to the microstructural change with respect to changes of film thickness. At a frequency of 1GHz, the hard-axis effective permeability decreases from 1252 to 1000 as the film thickness increases from 600 to 1200 nm, respectively. The VSM and MOKE results reveal an increase in magnetic anisotropy in the near-surface region of the film. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.