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Title: Strain induced room temperature ferromagnetism in epitaxial magnesium oxide thin films

We report on the epitaxial growth and room-temperature ferromagnetic properties of MgO thin films deposited on hexagonal c-sapphire substrates by pulsed laser deposition. The epitaxial nature of the films has been confirmed by both θ-2θ and φ-scans of X-ray diffraction pattern. Even though bulk MgO is a nonmagnetic insulator, we have found that the MgO films exhibit ferromagnetism and hysteresis loops yielding a maximum saturation magnetization up to 17 emu/cc and large coercivity, H{sub c} = 1200 Oe. We have also found that the saturation magnetization gets enhanced and that the crystallization degraded with decreased growth temperature, suggesting that the origin of our magnetic coupling could be point defects manifested by the strain in the films. X-ray (θ-2θ) diffraction peak shift and strain analysis clearly support the presence of strain in films resulting from the presence of point defects. Based on careful investigations using secondary ion mass spectrometer and X-ray photoelectron spectroscopy studies, we have ruled out the possibility of the presence of any external magnetic impurities. We discuss the critical role of microstructural characteristics and associated strain on the physical properties of the MgO films and establish a correlation between defects and magnetic properties.
Authors:
;  [1] ; ; ;  [2] ;  [3] ;  [4] ;  [5]
  1. Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)
  2. Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)
  3. Department of Mechanical Engineering, North Carolina A & T State University, Greensboro, North Carolina 27411 (United States)
  4. Princeton Institute for the Science and Technology of Materials (PRISM), Princeton University, Princeton, New Jersey 08540 (United States)
  5. Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709 (United States)
Publication Date:
OSTI Identifier:
22492874
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 16; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CRYSTALLIZATION; ENERGY BEAM DEPOSITION; EPITAXY; FERROMAGNETISM; LASER RADIATION; MAGNESIUM OXIDES; MAGNETIC PROPERTIES; MAGNETIZATION; POINT DEFECTS; PULSED IRRADIATION; SAPPHIRE; STRAINS; TEMPERATURE RANGE 0273-0400 K; THIN FILMS; X RADIATION; X-RAY DIFFRACTION; X-RAY PHOTOELECTRON SPECTROSCOPY