Site occupancy and magnetic properties of Al-substituted M-type strontium hexaferrite
- Department of Physics and Astronomy, Mississippi State University, Mississippi State, Mississippi 39762 (United States)
- Center for Computational Sciences, Mississippi State University, Mississippi State, Mississippi 39762 (United States)
- Department of Electrical and Computer Engineering and MINT Center, The University of Alabama, Tuscaloosa, Alabama 35487 (United States)
- Department of Physics, University of North Texas, Denton, Texas 76203 (United States)
- Thematic Unit of Excellence on Computational Materials Science, S.N. Bose National Centre for Basic Sciences, Sector-III, Block-JD, Salt Lake, Kolkata-700098 (India)
We use first-principles total-energy calculations based on density functional theory to study the site occupancy and magnetic properties of Al-substituted M-type strontium hexaferrite SrFe{sub 12−x}Al{sub x}O{sub 19} with x = 0.5 and x = 1.0. We find that the non-magnetic Al{sup 3+} ions preferentially replace Fe{sup 3+} ions at two of the majority spin sites, 2a and 12k, eliminating their positive contribution to the total magnetization causing the saturation magnetization M{sub s} to be reduced as Al concentration x is increased. Our formation probability analysis further provides the explanation for increased magnetic anisotropy field when the fraction of Al is increased. Although Al{sup 3+} ions preferentially occupy the 2a sites at a low temperature, the occupation probability of the 12k site increases with the rise of the temperature. At a typical annealing temperature (>700 °C) Al{sup 3+} ions are much more likely to occupy the 12k site than the 2a site. Although this causes the magnetocrystalline anisotropy K{sub 1} to be reduced slightly, the reduction in M{sub s} is much more significant. Their combined effect causes the anisotropy field H{sub a} to increase as the fraction of Al is increased, consistent with recent experimental measurements.
- OSTI ID:
- 22489444
- Journal Information:
- Journal of Applied Physics, Vol. 117, Issue 24; 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
Similar Records
Site preference and magnetic properties of Ga/In-substituted strontium hexaferrite: An ab initio study
Fluctuations in the local fields due to Al{sup 3+} ions substitution in the M-type barium hexaferrites, BaFe{sub 12{minus}x}Al{sub x}O{sub 12}