Structural and magnetic properties of (Zn,Fe)Te thin films grown by MBE under Zn-rich flux condition

We have performed the structural and magnetic characterization of Zn1-xFexTe thin films grown by molecular beam epitaxy (MBE). Thin films of Zn1-xFexTe with Fe composition up to x~0.06 were grown by MBE with the supply of excess Zn flux over Te flux. From the structural analyses by x-ray absorption fine structure (XAFS), it is revealed that the grown film with a low Fe content x=0.015 is composed of pure diluted phase with substitutional Fe atoms while the precipitation of an extrinsic phase is suggested at higher Fe contents x=0.03~0.06. The magnetization measurement reveals a clear distinction in the magnetic-field (M-H) and temperature (M-T) dependences between the low and high Fe contents; a hysteretic M-H dependence and the blocking phenomenon in the M-T dependence at the higher Fe content. These behaviors are attributed to the superparamagnetism, originating from the formation of an extrinsic precipitate.