Improving the morphological and magnetic properties of permalloy films by adopting ultra-low-pressure sputtering

A series of permalloy (NiFe) thin films of fixed thickness were grown by DC-sputtering at different argon pressures and without buffer layers. When the pressure was lowered from 1.2 Pa to 0.004 Pa, the coercivity decreased remarkably form 1353.5 A/m to 119.4 A/m. In addition, the NiFe film fabricated at ultra-low-pressure showed low damping, and its zero-field linewidth approached zero. Based on ferromagnetic resonance (FMR) and atomic force microscopy (AFM) observations, we attribute the excellent magnetic properties of NiFe film fabricated under ultra-low pressure to its improved morphological and magnetic uniformity.