Structural and electro-magnetic properties of high (BH) La-Sm substituted Sr-hexaferrite for brushless DC electric motors application

Impacts of Sol-Gel Auto-Combustion and Ultrasonication Approaches on Structural, Magnetic, and Optical Properties of Sm-Tm Co-Substituted Sr0.5Ba0.5Fe12O19 Nanohexaferrites: Comparative Study

“…In several earlier reports, it was claimed that the trend in M r depends principally on the tendency of M s and on the net alignments of grain magnetization caused by strong exchange interactions among nanoparticles (NPs) [29]. M-type hexaferrites comprise five different crystallographic sites of Fe 3+ ions-one bipyramidal site "2b" having spin-up direction, one tetrahedral site "4f1" having spin-down direction, and three octahedral sites amongst which "4f2" has spin-down direction and "12k" and "2a" have spin-up direction [30,31]. The magnetic moments of Fe 3+ ions are arranged collinearly because of the presence of super-exchange interactions.…”

“…At high substituting level, Tm 3+ and Sm 3+ ions can also reside in the 2a, 2b, and 12k sites (particularly the 12k site) having upward spins. The total number of unpaired M-type hexaferrites comprise five different crystallographic sites of Fe 3+ ions-one bipyramidal site "2b" having spin-up direction, one tetrahedral site "4f 1 " having spin-down direction, and three octahedral sites amongst which "4f 2 " has spin-down direction and "12k" and "2a" have spin-up direction [30,31]. The magnetic moments of Fe 3+ ions are arranged collinearly because of the presence of super-exchange interactions.…”

“…Moreover, Tm-Sm substituting ions improved the density of the produced samples up to x = 0.04 for the sol-gel approach and x = 0.03 for the ultrasonication route, as shown in the SEM study. This leads to improving the magnetic dipoles per unit volume; hence M s and M r rise with substitutions [30].…”

“…The total number of unpaired electrons is reduced, resulting in a drop in the values of magnetization. Furthermore, it has been reported that the larger content of rare earth ions gradually alters the magnetization from collinear spins to non-collinear spins of Fe 3+ ions, and hence decreases the magnetization [30,36]. Sadiq et al [36] claimed that the doping with RE elements could reduce the strength of super-exchange interactions among Fe 3+ -O-Fe 3+ , leading to spin-canting or non-collinear arrangement of magnetic moments.…”

Effect of Rare-Earth Co-Doping on the Microstructural and Magnetic Properties of BaFe12O19

“…In addition, co-doped Tm-Tb, Eu-Nd, Sm-Co Ba-hexaferrites have also been investigated and have been shown that co-doping of the rare-earth ions provides hexaferrites with a rise in the magnetization and/or coercivity [24][25][26][27]. Among other magnetic properties, some attempts have also been made to improve the maximum energy product, (BH)max for Srhexaferrites and Ba-hexaferrites using La-Sm [28,29].Researchers have different manufacturing methods to produce hexaferrites such as traditional ceramic methods [30][31][32][33][34] or several chemical methods [35][36][37][38][39][40][41].…”