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Magnetism of Amorphous and Nano-Crystallized Dc-Sputter-Deposited MgO Thin Films
Department of Materials Science, Tmfy-MSE, The Royal Institute of Technology, Stockholm SE100 44, Sweden
Department of Physics, Amrita Vishwa Vidyapeetham University, Amritapuri Campus, Kollam, Kerala 690525, India
School of Materials and Engineering, Anhui University of Technology, Maanshan 243002, China
Department of Physics, University of South Florida, Tampa, FL 33620, USA
Department of Physics, Government College, Kottayam, Kerala 686013, India
* Author to whom correspondence should be addressed.
Received: 13 June 2013; in revised form: 20 July 2013 / Accepted: 26 July 2013 / Published: 7 August 2013
Abstract: We report a systematic study of room-temperature ferromagnetism (RTFM) in pristine MgO thin films in their amorphous and nano-crystalline states. The as deposited dc-sputtered films of pristine MgO on Si substrates using a metallic Mg target in an O2 containing working gas atmosphere of (N2 + O2) are found to be X-ray amorphous. All these films obtained with oxygen partial pressure (PO2) ~10% to 80% while maintaining the same total pressure of the working gas are found to be ferromagnetic at room temperature. The room temperature saturation magnetization (MS) value of 2.68 emu/cm3 obtained for the MgO film deposited in PO2 of 10% increases to 9.62 emu/cm3 for film deposited at PO2 of 40%. However, the MS values decrease steadily for further increase of oxygen partial pressure during deposition. On thermal annealing at temperatures in the range 600 to 800 °C, the films become nanocrystalline and as the crystallite size grows with longer annealing times and higher temperature, MS decreases. Our study clearly points out that it is possible to tailor the magnetic properties of thin films of MgO. The room temperature ferromagnetism in MgO films is attributed to the presence of Mg cation vacancies.
Keywords: room temperature ferromagnetism; Mg vacancy; magnetron sputtering; O2 content; annealing
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Mahadeva, S.K.; Fan, J.; Biswas, A.; Sreelatha, K.S.; Belova, L.; Rao, K.V. Magnetism of Amorphous and Nano-Crystallized Dc-Sputter-Deposited MgO Thin Films. Nanomaterials 2013, 3, 486-497.
Mahadeva SK, Fan J, Biswas A, Sreelatha KS, Belova L, Rao KV. Magnetism of Amorphous and Nano-Crystallized Dc-Sputter-Deposited MgO Thin Films. Nanomaterials. 2013; 3(3):486-497.
Mahadeva, Sreekanth K.; Fan, Jincheng; Biswas, Anis; Sreelatha, K. S.; Belova, Lyubov; Rao, K. V. 2013. "Magnetism of Amorphous and Nano-Crystallized Dc-Sputter-Deposited MgO Thin Films." Nanomaterials 3, no. 3: 486-497.