Low-Frequency Alternative-Current Magnetic Susceptibility and Microstructure of Amorphous Co60Fe20V20 Thin Films

In this study, Co60Fe20V20 films were sputtered onto a glass substrate with various thicknesses from 3 to 13 nm at room temperature (RT). The microstructure and low-frequency alternative-current magnetic susceptibility (chi(ac)) were examined. Selected-area-diffraction (SAD) patterns and highresolution cross-sectional transmission electron microscopy (HRX-TEM) images demonstrated that the microstructure of the Co60Fe20V20 thin films was amorphous. Moreover, the magnetic property was investigated by measuring the films' low-frequency alternative-current magnetic susceptibility (chi(ac)). The maximum chi(ac) value decreased from 4.3 x 10(-3) to 1.8 x 10(-3) when the thickness was increased from 3 to 7 nm because the thinner amorphous films exhibited no magneto nanocrystalline anisotropy. Subsequently, the maximum chi(ac) value increased from 1.8 x 10(-3) to 3.4 x 10(-3) when the thickness was increased from 7 to 13 nm because of the spin exchange-coupling effect of the thicker CoFeV films. This suggests that the observed chi(ac) had a convex-up feature in the Co60Fe20V20 thin films. The maximum chi(ac) is associated with the highest spin sensitivity along with a corresponding optimal resonance frequency (f(res)). In this study, the optimal f(res) was lower than 3000 Hz, indicating that the Co60Fe20V20 films can be used for low-frequency magnetic recording media applications.