摘要
The present study investigates the influence of La<sup>3+</sup> and Pr<sup>3+</sup> doping on the structural, magnetic properties, and hyperfine fields of Sr<sub>0.7</sub>RE<sub>0.3</sub>Fe<sub>12-2x</sub> Co<sub>x</sub>Al<sub>x</sub>O<sub>19</sub>, (RE: La<sup>3+</sup> and Pr<sup>3+</sup>, <em>x</em> = 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 <em>x</em>. The room temperature magnetic study shows that for the Pr<sup>3+</sup> doped Sr<sub>0.7</sub>Pr<sub>0.3</sub>Fe<sub>12-2x</sub> Co<sub>x</sub>Al<sub>x</sub>O<sub>19</sub> (Pr<sup>3+</sup>-SrM), the magnetization value monotonically decreases while for La<sup>3+</sup> doped Sr<sub>0.7</sub>La<sub>0.3</sub>Fe<sub>12-2x</sub>Co<sub>x</sub>Al<sub>x</sub>O<sub>19</sub> (La<sup>3+</sup>-SrM) magnetization value shows a noticeable increase in magnetization value with <em>x</em>. The coercivity of the Pr<sup>3+</sup>-SrM compound was observed to decrease while that of the La<sup>3+</sup>-SrM compound showed a marked 40% increase at <em>x</em> = 0.2 (~5829 Oe) in comparison to undoped SrFe<sub>12</sub>O<sub>19</sub> (~3918 Oe). A difference in Curie temperature was also observed, with Tc ~ 525<span style="white-space:nowrap;">°</span>C at <em>x</em> = 0.4 for Pr<sup>3+</sup>-SrM and Tc = 505<span style="white-space:nowrap;">°</span>C for <em>x</em> = 0.4 for La<sup>3+</sup>-SrM compound. The observed differences in magnetic properties have been explained on the basis of the site occupancy of Co<sup>2+</sup> and Al<sup>3+</sup> in the presence of rare-earth ions. The presence of non-magnetic rare-earth ion, La<sup>3+</sup>, improved saturation magnetization, and coercivity and deemed suitable replacement for Sr<sup>2+</sup>. The hyperfine parameters namely quadrupole shift showed a decrease with the La3<sup>+</sup> or Pr<sup>3+</sup> doping independent of (Co<sup>2+</sup>-Al<sup>3+</sup>) ions doping. Overall, the Mossbauer analysis suggests that the (Co<sup>2+</sup>-Al<sup>3+</sup>) impurities prefer occupancy at 2<em>a</em> site.
The present study investigates the influence of La<sup>3+</sup> and Pr<sup>3+</sup> doping on the structural, magnetic properties, and hyperfine fields of Sr<sub>0.7</sub>RE<sub>0.3</sub>Fe<sub>12-2x</sub> Co<sub>x</sub>Al<sub>x</sub>O<sub>19</sub>, (RE: La<sup>3+</sup> and Pr<sup>3+</sup>, <em>x</em> = 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 <em>x</em>. The room temperature magnetic study shows that for the Pr<sup>3+</sup> doped Sr<sub>0.7</sub>Pr<sub>0.3</sub>Fe<sub>12-2x</sub> Co<sub>x</sub>Al<sub>x</sub>O<sub>19</sub> (Pr<sup>3+</sup>-SrM), the magnetization value monotonically decreases while for La<sup>3+</sup> doped Sr<sub>0.7</sub>La<sub>0.3</sub>Fe<sub>12-2x</sub>Co<sub>x</sub>Al<sub>x</sub>O<sub>19</sub> (La<sup>3+</sup>-SrM) magnetization value shows a noticeable increase in magnetization value with <em>x</em>. The coercivity of the Pr<sup>3+</sup>-SrM compound was observed to decrease while that of the La<sup>3+</sup>-SrM compound showed a marked 40% increase at <em>x</em> = 0.2 (~5829 Oe) in comparison to undoped SrFe<sub>12</sub>O<sub>19</sub> (~3918 Oe). A difference in Curie temperature was also observed, with Tc ~ 525<span style="white-space:nowrap;">°</span>C at <em>x</em> = 0.4 for Pr<sup>3+</sup>-SrM and Tc = 505<span style="white-space:nowrap;">°</span>C for <em>x</em> = 0.4 for La<sup>3+</sup>-SrM compound. The observed differences in magnetic properties have been explained on the basis of the site occupancy of Co<sup>2+</sup> and Al<sup>3+</sup> in the presence of rare-earth ions. The presence of non-magnetic rare-earth ion, La<sup>3+</sup>, improved saturation magnetization, and coercivity and deemed suitable replacement for Sr<sup>2+</sup>. The hyperfine parameters namely quadrupole shift showed a decrease with the La3<sup>+</sup> or Pr<sup>3+</sup> doping independent of (Co<sup>2+</sup>-Al<sup>3+</sup>) ions doping. Overall, the Mossbauer analysis suggests that the (Co<sup>2+</sup>-Al<sup>3+</sup>) impurities prefer occupancy at 2<em>a</em> site.
作者
Madhav L. Ghimire
Dom L. Kunwar
Jiba N. Dahal
Dipesh Neupane
Sunghyun Yoon
Sanjay R. Mishra
Madhav L. Ghimire;Dom L. Kunwar;Jiba N. Dahal;Dipesh Neupane;Sunghyun Yoon;Sanjay R. Mishra(Department of Physics and Materials Science, The University of Memphis, Memphis, TN, USA;Department of Physics, Virginia Commonwealth University, Richmond, VA, USA;Department of Physics, Kent State University, Kent, OH, USA;Department of Physics and Astronomy, Truman State University, Kirksville, MO, USA;Department of Physics, Gunsan National University, Gunsan, South Korea)
