Structural and dynamical magnetic response of co-sputtered Co_2FeAI heusler alloy thin films grown at different substrate temperatures

摘要

The interdependence between the dynamical magnetic response and the microstructural properties such as crystallinity, lateral crystallite size, structural ordering of the co-sputtered polycrystalline Co_2FeAl thin films on Si (100) are studied by varying the growth temperature from room temperature (RT) to 600 ℃. Frequency (7-11 GHz) dependent in-plane ferromagnetic resonance (FMR) studies were carried out by using co-planar waveguide to estimate Gilbert damping constant (a) and effective saturation magnetization (4πM_(eff)). The improvement in crystallinity, larger crystallite and particle sizes of the films are critical in obtaining films with lower α and higher (4πM_(eff)). Increase in the lattice constant with substrate temperature indicates the improvement in the structural ordering at higher temperatures. Minimum value of α is found to be 0.005 ± 0.0003 for the film deposited at 500 ℃, which is comparable to the values reported for epitaxial Co_2FeAl films. The value of (4πM_(eff)) is found to increase from 1.32 to 1.51 T with the increase in deposition temperature from RT to 500 ℃. The study also shows that the root mean square (rms) roughness linearly affects the FMR in-homogenous line broadening and the anisotropy field.