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Title: Modification of structure and magnetic anisotropy of epitaxial CoFe₂O₄ films by hydrogen reduction

Heteroepitaxial CoFe₂O₄ (CFO) thin films with different thicknesses were deposited on MgO (001) substrates. The as-deposited CFO films show a clear switching of magnetic anisotropy with increasing film thickness. The thinner films (<100 nm) show a perpendicular magnetic anisotropy due to the out-of-plane compressive strain. The thicker films exhibit an in-plane easy axis owing to the dominating shape anisotropy effect. The magnetostriction coefficient of CFO films is estimated to be λ[001] =-188 × 10⁻⁶. Metallic CoFe₂ films were obtained by annealing the as-deposited CFO films in forming gas (Ar 93% + H₂ 7%) at 450 °C. XRD shows that CoFe₂ films are textured out-of-plane and aligned in-plane, owing to lattice matching between CoFe₂ and MgO substrate. TEM results indicate that as-deposited films are continuous while the annealed films exhibit a nanopore mushroom structure. The magnetic anisotropy of CoFe₂ films is dominated by the shape effect. The results demonstrate that hydrogen reduction can be effectively used to modify microstructures and physical properties of complex metal oxide materials.
Authors:
 [1] ;  [2] ;  [1] ;  [2] ;  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Center for Integrated Nanotechnologies (CINT)
  2. Univ. of Texas, Arlington, TX (United States). Dept. of Physics
Publication Date:
OSTI Identifier:
1193448
Report Number(s):
LA/UR--15-20894
Journal ID: ISSN 0003-6951; APPLAB
Grant/Contract Number:
AC52-06NA25396; W911NF-11-1-0507
Type:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 106; Journal Issue: 11; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Research Org:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE magnetic anisotropy; magnetic films; epitaxy