Author(s)

Madhav L. Ghimire^1,2*, Dom L. Kunwar³, Jiba N. Dahal⁴, Dipesh Neupane¹, Sunghyun Yoon⁵, Sanjay R. Mishra¹

¹Department of Physics and Materials Science, The University of Memphis, Memphis, TN, USA.
²Department of Physics, Virginia Commonwealth University, Richmond, VA, USA.
³Department of Physics, Kent State University, Kent, OH, USA.
⁴Department of Physics and Astronomy, Truman State University, Kirksville, MO, USA.
⁵Department of Physics, Gunsan National University, Gunsan, South Korea.

The present study investigates the influence of La³⁺ and Pr³⁺ doping on the structural, magnetic properties, and hyperfine fields of Sr_0.7RE_0.3Fe_12-2x Co_xAl_xO₁₉, (RE: La³⁺ and Pr³⁺, x = 0.0 - 0.8) hexaferrite compounds prepared via auto-combustion technique. The XRD analysis shows a linear decrease in a and c lattice and unit cell volume contraction with the content x. The room temperature magnetic study shows that for the Pr³⁺ doped Sr_0.7Pr_0.3Fe_12-2x Co_xAl_xO₁₉ (Pr³⁺-SrM), the magnetization value monotonically decreases while for La³⁺ doped Sr_0.7La_0.3Fe_12-2xCo_xAl_xO₁₉ (La³⁺-SrM) magnetization value shows a noticeable increase in magnetization value with x. The coercivity of the Pr³⁺-SrM compound was observed to decrease while that of the La³⁺-SrM compound showed a marked 40% increase at x = 0.2 (~5829 Oe) in comparison to undoped SrFe₁₂O₁₉ (~3918 Oe). A difference in Curie temperature was also observed, with Tc ~ 525°C at x = 0.4 for Pr³⁺-SrM and Tc = 505°C for x = 0.4 for La³⁺-SrM compound. The observed differences in magnetic properties have been explained on the basis of the site occupancy of Co²⁺ and Al³⁺ in the presence of rare-earth ions. The presence of non-magnetic rare-earth ion, La³⁺, improved saturation magnetization, and coercivity and deemed suitable replacement for Sr²⁺. The hyperfine parameters namely quadrupole shift showed a decrease with the La3⁺ or Pr³⁺ doping independent of (Co²⁺-Al³⁺) ions doping. Overall, the Mossbauer analysis suggests that the (Co²⁺-Al³⁺) impurities prefer occupancy at 2a site.

Doped Hexaferrite, M-Type Hexaferrite, X-Ray Diffraction, Mossbauer

Ghimire, M. , Kunwar, D. , Dahal, J. , Neupane, D. , Yoon, S. and Mishra, S. (2020) Co-Doped Rare-Earth (La, Pr) and Co-Al Substituted M-Type Strontium Hexaferrite: Structural, Magnetic, and Mossbauer Spectroscopy Study. Materials Sciences and Applications, 11, 474-493. doi: 10.4236/msa.2020.117033.