Ferromagnetic Ge1-xMx (M = Mn, Co, and Fe) Nanowires
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1032-I14-05
Ferromagnetic Ge1-xMx (M = Mn, Co, and Fe) Nanowires Yong Jae Cho1, chang hyun Kim2, and jeunghee Park2 1
Department of Material Chemistry, Korea University, In the building of school of life science and biotechnilogy Rm #235, 5-ka,Anam-dong Sungbuk-ku Seou, Seoul, 136-701, Korea, Republic of 2
Department of Material Chemistry, Korea University, in the building of school of life science and biotechnology Rm#235 5-ka, Anam-dong Sungbuk-ku, Seoul, 136-701, Korea, Republic of
Ferromagnetic Ge1-xMx (M = Mn, Fe, and Co) Nanowires Yong Jae Jo, Seong-Hun Park, Wang Soo Lee, Chang Hyun Kim, Han Sung Kim, and Jeunghee Parka) Seung Yong Bae, Bongsoo Kim, Jae-Young Kim
ABSTRACT We synthesized Ge and Ge1-xMx (M = Mn, Co, and Fe, x ≤ 0.2) nanowires using thermal vapour transport method. All nanowires consisted of single-crystalline Ge nanocrystals grown uniformly with the [111] direction. High-resolution X-ray diffraction pattern shows no cluster formation for all Ge1-xMx nanowires. The Mn and Fe doping decreases the lattice constant, but not Co doping. X-ray absorption spectroscopy and X-ray magnetic circular dichroism measurement revealed that the Mn2+ and Fe2+ ions preferentially occupy the tetrahedral sites, substituting for Ge. We suggest that the Mn or Fe ions produce dopant-acceptor hybridization with host defects in p-type Ge, but not Co ions. The magnetic moment of Mn2+ ions reaches a maximum for x = ~ 0.1, which is much larger than that of the Fe2+ ions. The magnetization measurement also confirms the roomtemperature ferromagnetism of Mn-doped Ge nanowires, which is maximized at x = ~ 0.1. We conclude that the Mn ions are most efficiently doped into the Ge nanowires to form a ferromagnetic semiconductor. INTODUCTION Dilute magnetic semiconductors (DMS) that are obtained by doping semiconductor materials with magnetic impurities have been investigated extensively due to their potential application in spintronic devices.1 Among various types of DMSs, the Ge-based DMS have recently attracted special attention, which is mainly due to its potential integration with conventional Si-based electronic devices. The intensive experimental studies of Ga1-xMnx single crystals and nanocrystalline thin films reported a wide range of TC from 116 K to 350 K.2-12 It was suggested that secondary phases such as Ge8Mn11 or Ge3Mn5 alloys, rather than isolated Mn impurities, can be attributed to their ferromagnetism.6-10 Despite such conflicting origin of the ferromagnetism, the Ge-DMSs are still very promising materials for spintronic devices operating at high temperature. Herein, we report the synthesis of Ge1-xMx (M = Mn, Fe, and Co, x ≤0.2) NWs; Ge (1), G0.95Mn0.05 (2), Ge0.9Mn0.1(3), Ge0.8Mn0.2 (4), Ge0.9Fe0.1 (5), Ge0.9Co0.1 (6) NWs, and Ge0.6Co0.4 (7) NWs, by the vapor transport method. The lattice constants and electronic structures were thoroughly investigated by high-resolution X-ray diffraction (XRD), Raman spectroscopy,
X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and X-ray magne
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