Strain induced room temperature ferromagnetism in epitaxial magnesium oxide thin films
- Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)
- Department of Mechanical Engineering, North Carolina A & T State University, Greensboro, North Carolina 27411 (United States)
- Princeton Institute for the Science and Technology of Materials (PRISM), Princeton University, Princeton, New Jersey 08540 (United States)
- Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709 (United States)
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.
- OSTI ID:
- 22492874
- Journal Information:
- Journal of Applied Physics, Vol. 118, Issue 16; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
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