Ferromagnetic coupling and the effect of Fe-d t2g state on ferromagnetism in half-metallic ZnO:Fe
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ORIGINAL ARTICLE
Ferromagnetic coupling and the effect of Fe‑dt2g state on ferromagnetism in half‑metallic ZnO:Fe D. Saikia1 · Hemant Kumar1 · J. P. Borah1 Received: 5 December 2019 / Accepted: 30 September 2020 © Islamic Azad University 2020
Abstract Based on first principle calculations using GGA + U approach, we have studied the origin of room-temperature ferromagnetism in Fe-doped ZnO. The ferromagnetic coupling and the contribution of Fe-d states on the ferromagnetism of ZnO are also studied. The p–d exchange interaction between the Fe-d and O-p states is responsible for the ferromagnetism at lower Fe concentration in ZnO; whereas at the higher concentration, the enhanced short-range antiferromagnetic coupling between Fe ions dominates over ferromagnetism. The DOS results depict that the Fe-dt2g state predominantly contributes the hybridization at the fermi level resulting the magnetism in the Fe-doped ZnO system. The total energy calculations reveal the existence of short-range ferromagnetic coupling in the system. The band structure results depict the half-metallic character of the system with spin-polarized nature. Keywords Nanoparticles · Magnetic materials · Diluted magnetic semiconductors · Half-metallic
Introduction Diluted magnetic semiconductors (DMS) have been perceptive materials in the recent years with greater applications in spintronic devices due to their remarkable spin-polarized property [1, 2]. To enhance the performances of spintronic devices such as magnetic storages and sensors, researchers have been focusing on transition metal (Fe, Mn, Ni, Co, etc.)-doped DMSs [3–5]. Doping of transition metal elements into the semiconducting materials produces magnetic coupling by inducing spin polarization, which is one of the key requirements of spintronic devices [6, 7]. Among all DMSs, ZnO-based DMSs have been an extensive candidate due to their unique optical characteristics such as higher band gap (3.4 eV) which are suitable for LEDs, solar cells, UV semiconductor lasers, etc.[8, 9]. It is essential to recognize the physical mechanisms responsible for the room-temperature ferromagnetism (RTFM) in these materials from both fundamental and technological perspective. Being a superior ferromagnetic transition metal with high Curie temperature, it is efficient to use Fe as a doping agent * D. Saikia [email protected] 1
Department of Physics, National Institute of Technology Nagaland, Chumukedima, Dimapur, Nagaland 797103, India
in ZnO to introduce ferromagnetism into it [10, 11]. The exchange interactions between the unfilled d states of Fe contributes the RTFM in Fe-doped ZnO. Mihalache et al. [12] studied magnetism in Fe-doped ZnO nanoparticles and observed the effect of Ruderman–Kittel–Kasuya–Yosida (RKKY) exchange interactions on the RTFM in the system. Abdel-Baset et al. [13] studied magnetic properties of Fe doped ZnO and observed RTFM due to the exchange interactions between the Fe atoms and enhanced antiferromagnetic interactions at higher doping concentration of Fe. They also o
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