title: Magnetism of Amorphous and Nano-Crystallized Dc-Sputter-Deposited MgO Thin Films.
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 MSvalues 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, MSdecreases. 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.
authors.affiliation: Department of Materials Science, Tmfy-MSE, The Royal Institute of Technology, Stockholm SE100 44, Sweden. skm@kth.se.|Department of Physics, Amrita Vishwa Vidyapeetham University, Amritapuri Campus, Kollam, Kerala 690525, India. skm@kth.se.
authors.forename: Sreekanth K
authors.initials: SK
authors.lastname: Mahadeva
authors.affiliation: Department of Materials Science, Tmfy-MSE, The Royal Institute of Technology, Stockholm SE100 44, Sweden. fanjincheng2006@yahoo.com.cn.|School of Materials and Engineering, Anhui University of Technology, Maanshan 243002, China. fanjincheng2006@yahoo.com.cn.
authors.forename: Jincheng
authors.initials: J
authors.lastname: Fan
authors.affiliation: Department of Materials Science, Tmfy-MSE, The Royal Institute of Technology, Stockholm SE100 44, Sweden. biswas.anis@gmail.com.|Department of Physics, University of South Florida, Tampa, FL 33620, USA. biswas.anis@gmail.com.
authors.forename: Anis
authors.initials: A
authors.lastname: Biswas
authors.affiliation: Department of Physics, Amrita Vishwa Vidyapeetham University, Amritapuri Campus, Kollam, Kerala 690525, India. kssreelatha@yahoo.com.|Department of Physics, Government College, Kottayam, Kerala 686013, India. kssreelatha@yahoo.com.
authors.forename: K S
authors.initials: KS
authors.lastname: Sreelatha
authors.affiliation: Department of Materials Science, Tmfy-MSE, The Royal Institute of Technology, Stockholm SE100 44, Sweden. lyuba@kth.se.
authors.forename: Lyubov
authors.initials: L
authors.lastname: Belova
authors.affiliation: Department of Materials Science, Tmfy-MSE, The Royal Institute of Technology, Stockholm SE100 44, Sweden. rao@kth.se.
authors.forename: K V
authors.initials: KV
authors.lastname: Rao
keywords: Mg vacancy; O2 content; annealing; magnetron sputtering; room temperature ferromagnetism