Impact of growth conditions on the structural and magnetic properties of (Zn,Fe)Te thin films grown by molecular beam epitaxy (MBE)

Abstract

We have investigated the effect of growth conditions on the structural and magnetic properties of (Zn,Fe)Te. Thin films of Zn1-xFexTe are grown by molecular beam epitaxy (MBE) with an almost same Fe composition, x = 1.4% but under two different growth conditions: (a) Te-rich (Te/Zn flux ratio of 2.3) and (b) Zn-rich (Te/Zn flux ratio of 0.7). Structural analysis by using x-ray absorption fine structure (XAFS) reveals that both films are mainly composed of pure diluted phase with substitutional Fe atoms on the Zn-site, but the valence state of Fe atoms in the film grown under Zn-rich condition has deviated more from isoelectronic Fe2+ as compared to the one grown in Te-rich condition. Accordingly, the magnetization measurement using SQUID confirms a significant difference in magnetic properties among these films; a linear dependence of magnetization on magnetic field (M−H), typical of van-Vleck paramagnetism under Te-rich growth condition turns into ferromagnetic behaviors with hysteretic M−H curve in the Zn-rich condition. The ferromagnetism exhibited by the Zn-rich growth film may reflect the deviation of substitutional Fe valence state from Fe2+ to Fe2+/3+ mixed states.