Columnar growth structure dependent soft magnetic and electrical transport properties of Co nanocrystalline films evaporated with a high magnetic field

Abstract

Control and improvement of the magnetic and electrical properties of magnetic nanocrystalline films are very essential for their applications in spintronics and magnetic storages. This paper studies the effects of high magnetic field (HMF) on the microstructure, soft magnetic and electrical transport properties of the Co nanocrystalline films. It was found that the Co films without HMF were disordered stack of spherical nanoparticles. The stack changed to columnar structure with the HMF application. Furthermore, this columnar crystal changed to columnar stack of spherical nanoparticles with the increase of evaporation temperature under HMF. HMF induced a part of the c-axis preferred orientation in the Co films aligning along the direction of HMF. The varied growth structure and preferred orientation led to the change from the in-plane magnetic anisotropy (without HMF) to isotropy in the Co films due to the application of HMF at a higher evaporation temperature. The saturation magnetization of the Co films with columnar crystals obtained by HMF was much larger than that of the films composed of spherical nanoparticles because of the dense atom arrangement. The decrease of the grain boundaries due to the changed growth structure under HMF remarkably reduced the coercivity and resistivity of the Co films. The changed growth structure under HMF also induced and improved the in-plane anisotropic magnetoresistance of the Co films. These results indicate that the adjustment of columnar growth structure by HMF effectively control and improve the soft magnetic and electrical transport properties of the Co films.