Structural and Magnetic Properties of Nitrogen Acceptor Co-doped (Zn,Fe)Te Thin Films Grown in Zn-Rich Condition by Mole
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https://doi.org/10.1007/s11664-020-08311-7 2020 The Minerals, Metals & Materials Society
Structural and Magnetic Properties of Nitrogen Acceptor Co-doped (Zn,Fe)Te Thin Films Grown in Zn-Rich Condition by Molecular Beam Epitaxy (MBE) INDRAJIT SAHA,1 YUTA TOMOHIRO,1 KEN KANAZAWA,1 HIROAKI NITANI,2 and SHINJI KURODA 1,3 1.—Institute of Materials Science, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba 305-8573, Japan. 2.—High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan. 3.—e-mail: [email protected]
We have investigated the structural and magnetic properties of (Zn,Fe)Te:N thin films grown under Zn-rich condition with Fe composition fixed at 1.4% and N concentrations varying in the range [N] = 1.8 9 1018–5.1 9 1019 cm 3. Structural analysis by x-ray diffraction (XRD) detects some additional extrinsic diffraction peaks possibly from Fe-N compounds in the N-doped film with [N] = 5.1 9 1019 cm 3 only. Accordingly, x-ray absorption fine structure (XAFS) analysis reveals the shifting of Fe atoms from substitutional position for N-doped films with high N concentrations, [N] ‡ 1.8 9 1019 cm 3, whereas N-doped films with intermediate N concentrations [N] £ 4.3 9 1018 cm 3 are composed of pure diluted phase with substitutional Fe atoms in the valence state deviating from Fe2+. Magnetization measurement using SQUID confirms drastic change of magnetic properties; the linear dependence of magnetization on magnetic field, typical of van Vleck-type paramagnetism in the film without N-doping changes into room temperature ferromagnetic behaviors with hysteretic magnetization curves for N-doped films. The observed weak room temperature ferromagnetic behavior of the N-doped films with [N] £ 4.3 9 1018 cm 3 may reflect the deviation of substitutional Fe valence state from Fe2+ to Fe2+/3+ mixed states. On the other hand, the robust room temperature ferromagnetic behavior exhibited by N-doped films with [N] ‡ 1.8 9 1019 cm 3 may originate from precipitates of Fe-N compounds with Fe being in Fe2+/3+ or other valence state. Key words: Molecular beam epitaxy, tellurides, magnetic materials, room temperature ferromagnetism
INTRODUCTION Diluted magnetic semiconductors (DMSs) comprise the family of standard semiconductors in which a sizable portion of atoms are substituted by such elements that provide localized magnetic moments in the semiconductor matrix. Usually, magnetic moments originate from the unfilled 3d or 4f shells of transition metals or rare earths
(Received March 20, 2020; accepted June 30, 2020)
(lanthanides), respectively. In particular, DMSs exhibiting room temperature ferromagnetic behavior are considered to be prominent materials on the perspective of both materials science and applications for spintronics.1 Therefore, research on DMSs consisting of various combinations of host semiconductors and magnetic elements are ongoing to identify a new candidate for high-temperature ferromagnetic DMSs.2–4 Some have already been reported to exhibit ferromagnetism at room temperature. B
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