Effects of high-temperature annealing on magnetic properties of (Zn0.91Mn0.09)O thin films grown by RF magnetron sputtering

Abstract

The (Zn0.91Mn0.09)O thin film annealed at 1000 degrees C for 60 min in N-2 atmosphere showed two kinds of Curie temperature (T-C) values of T-C1 around 130 K and T-C2 above 300 K while the as-grown (Zn0.91Mn0.09)O thin film showed typical ferromagnetism with the T-C of 108 K. It is expected that the increase of T-C up to T-C1 might be attributed to the enhancement of crystal magnetic anisotropy because the increases of (0001) peak for X-ray diffraction patterns and Mn2+-related emission for photoluminescence spectra were observed for annealed (Zn0.91Mn0.09)O thin films. The increase of T-C above T-C2 might be originated from the formation of nano-sized (Zn0.91Mn0.09)O islands because it was confirmed that the nano-sized (Zn(0.91)Mno(0.09))O islands were formed after annealing treatment and that they revealed clearly the magnetic domains at 300 K for the measurements of atomic force microscopy and magnetic force microscopy, respectively. The room temperature ferromagnetism in the nano-sized (Zn0.91Mn0.09)O islands is considered to be originated from the inhomogeneous distribution of Mn ions.