Co-Doped Rare-Earth (La, Pr) and Co-Al Substituted M-Type Strontium Hexaferrite: Structural, Magnetic, and Mossbauer Spectroscopy Study

Abstract

The present study investigates the influence of La 3+ and Pr 3+ doping on the structural, magnetic properties, and hyperfine fields of Sr 0.7 RE 0.3 Fe 12−2x Co x-Al x O 19 , (RE: La 3+ and Pr 3+ , 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 Pr 3+ doped Sr 0.7 Pr 0.3 Fe 12−2x Co x Al x O 19 (Pr 3+-SrM), the magnetization value monotonically decreases while for La 3+ doped Sr 0.7 La 0.3 Fe 12−2x Co x Al x O 19 (La 3+-SrM) magnetization value shows a noticeable increase in magnetization value with x. The coercivity of the Pr 3+-SrM compound was observed to decrease while that of the La 3+-SrM compound showed a marked 40% increase at x = 0.2 (~5829 Oe) in comparison to undoped SrFe 12 O 19 (~3918 Oe). A difference in Curie temperature was also observed, with Tc ~ 525˚C at x = 0.4 for Pr 3+-SrM and Tc = 505˚C for x = 0.4 for La 3+-SrM compound. The observed differences in magnetic properties have been explained on the basis of the site occupancy of Co 2+ and Al 3+ in the presence of rare-earth ions. The presence of non-magnetic rare-earth ion, La 3+ , improved saturation magnetization, and coercivity and deemed suitable replacement for Sr 2+. The hyperfine parameters namely quadrupole shift showed a decrease with the La 3+ or Pr 3+ doping independent of (Co 2+-Al 3+) ions doping. Overall, the Mossbauer analysis suggests that the (Co 2+-Al 3+) impurities prefer occupancy at 2a site.

MECHANOSYNTHESIS, CRYSTAL STRUCTURE, MAGNETIC AND ABSORPTION PROPERTIES OF Al SUBSTITUTED BaFe12O19

“…It is observed that there is a significant fall in Hc from 4.20kOe at Al content (x) = 0 to Hc = 3.13 kOe and Hc = 2.85kOe for BAl-2 and BAl-4 samples, respectively. The coercivity decreased with the increase in Al 3+ content due to decrease in magneto-crystalline anisotropy [3,8,10,13]. Our results on the magnetic properties of Al 3+ substituted BaFe(12-x)AlxO19 M-type ferrite for x = 2.0, and x = 4.0 are in good agreement with those already reported for the substituted barium hexaferrite (Al, Cr) [15].…”

“…Consequently, a decrease in Hc with an increase in Al 3+ content is expected behavior for a magnetic microwave absorber application. The reflection loss of electromagnetic wave (for the case of a metal-backed single layer) can be calculated through the mathematical equation approach as follows: …………..... (2) with Zin given by = …..………… (3) where r and r are the complex magnetic permeability and electric permittivity of the medium, c is the velocity of light in free space, f is the frequency and d is the absorber thickness [1,8]. The variation in reflection loss (RL) with frequency for all samples of 2.0 mm thickness in the frequency range of 9.0-13 GHz is shown in Figure 7.…”

“…Numerous papers have been reported on the study of structural, magnetic and microwave absorption properties. They explained that the structural, magnetic and absorption properties of BaFe12O19 can be improved by substituting Fe with ions such as Zn, Ti, Mn, Cr, La and Al [2,3,[7][8][9][10][11].…”

Recent Progress in Hexagonal Ferrites Based Composites for Microwave Absorption

“…[215] Efforts have been made to enhance the magnetic characteristics of hexaferrite by cationic substitution to meet a variety of applications. [148,216] These includes efforts on altering the intrinsic properties of hexaferrites by replacing with either single or multiple trivalent metal ions such as La 3+ , [217][218][219][220][221] Tb 3+ , [222,223] Nd 3+ , [138][139][140][224][225][226] Eu 3+ , [227] Dy 3+ , [228,229] Sm 3+ , [230,231] Cr 3+ , [232,233] Al 3+ , [185,186,234,235] Gd 3+ , [236][237][238] Sc 3+ , [239] Er 3+ , [240][241][242] Pr 3+ , [243] Yb 3+ , [244] Ce 3+ , [245] La 3+ -Pr 3+ , [246] La 3+ -Nd 3+ , [247] Nd 3+ -Sm 3+ , [248] Nb 3+ -Y 3+ , [249] La 3+ -Ce 3+ , [250] Er 3+ -Cr 3+ , [251] Dy 3+ -Nd 3+ -Pr 3+ [252] or a suitable mix of divalent and trivalent ions such as Tb 3+ -Mn 2+ , …”

Effect of the neodymium doping on the magnetic and structural properties of the Sr-hexaferrite obtained by the Pechini method

“…These improvements can be achieved by doping with rare earth trivalent cations, for example, Nd 3+ [15][16][17][18]. La 3+ [19,20], Pr 3+ [21,22], and Gd 3+ [23]. These elements are the most studied and therefore have had the greatest impact on various investigations although there are more possibilities of rare earth for doping such as Sm 3+ , Er 3+ , Yb 3+ , Eu 3+ , and Dy 3+ [24,25].…”