Spin reorientation phenomena in selected rare earth-transition metal intermetallics

Spin reorientation phenomena in selected rare earth-transition metal intermetallic compounds have been studied in the temperature range from 20K to their T{dollar}sb{lcub}rm c{rcub}{dollar} employing magnetic susceptibility measurements. The compounds included in this study are the RCo{dollar}sb5{dollar} (R = Sm, Gd, Tb, Dy, Ho and Er), Pr{dollar}sb2{dollar}Co{dollar}sb{lcub}rm 17-x{rcub}{dollar}Fe{dollar}sb{lcub}rm x{rcub}{dollar} (0 {dollar}leq{dollar} x {dollar}leq{dollar} 17), RTiFe{dollar}sb{lcub}11{rcub}{dollar}(R = Tb, Dy, Ho and Er) and Nd{dollar}sb{lcub}0.5{rcub}{dollar}Er{dollar}sb{lcub}1.5{rcub}{dollar}Fe{dollar}sb{lcub}rm 14-x{rcub}{dollar}M{dollar}sb{lcub}rm x{rcub}{dollar}B (M = Co or Al and x = 0, 1, 2 and 3). The effect of spin reorientation transition on the remanence and the intrinsic coercivity of Nd{dollar}sb2{dollar}Fe{dollar}sb{lcub}14{rcub}{dollar}B magnets of various textures have also been investigated in the temperature range between 4.2 and 273K in external magnetic fields up to 90 kOe.; The magnetic anisotropy of R{dollar}sb{lcub}rm m{rcub}{dollar}T{dollar}sb{lcub}rm n{rcub}{dollar} compounds arises from the rare earth sublattice and the transition metal sublattice. The anisotropy of the rare earth sublattice arises from the crystal field effects in the rare earth ions and the rare earth-transition metal exchange interaction. The anisotropy of the transition metal sublattice is very complicated and is treated phenomenologically in this work. The magnetic anisotropy of R{dollar}sb{lcub}rm m{rcub}{dollar}T{dollar}sb{lcub}rm n{rcub}{dollar} compounds may be altered by modifying (1) the rare earth crystal field effect, or (2) the rare earth-transition metal exchange interaction or (3) the anisotropy of transition metal sublattice. These modifications can be achieved by incorporating the atoms either substitutionally or interstitially in a crystal structure. The examples for the former are the Pr{dollar}sb{lcub}rm 1-x{rcub}{dollar}R{dollar}sb{lcub}rm x{rcub}{dollar}Co{dollar}sb{lcub}5 + delta{rcub}{dollar}, the Pr{dollar}sb2{dollar}Co{dollar}sb{lcub}rm 17-x{rcub}{dollar}Fe{dollar}sb{lcub}rm x{rcub}{dollar} or the Nd{dollar}sb{lcub}0.5{rcub}{dollar}Er{dollar}sb{lcub}1.5{rcub}{dollar}Fe{dollar}sb{lcub}rm 14-x{rcub}{dollar}M{dollar}sb{lcub}rm x{rcub}{dollar}B systems and that for the latter are Sm{dollar}sb2{dollar}Fe{dollar}sb{lcub}17{rcub}{dollar}N{dollar}sb{lcub}rm x{rcub}{dollar} or Sm{dollar}sb2{dollar}Fe{dollar}sb{lcub}17{rcub}{dollar}C{dollar}sb{lcub}rm x{rcub}{dollar} compounds. The substitutional type of modification of rare earth crystal field effect can be achieved by replacing rare earth(s) of opposite or of the same sign but different magnitude of second order Stevens' coefficient in the rare earth sublattice or by changing the transition metal partner through the preferential site occupation in the transition metal sublattice. The examples for the substitution type are the (Pr{dollar}sb{lcub}rm 1-x{rcub}{dollar}R{dollar}sb{lcub}rm x{rcub}{dollar})Co{dollar}sb5{dollar} compounds and Pr{dollar}sb2{dollar}Co{dollar}sb{lcub}rm 17-x{rcub}{dollar}Fe{dollar}sb{lcub}rm x{rcub}{dollar} compounds. Examples for the interstitial type are the Sm{dollar}sb2{dollar}Fe{dollar}sb{lcub}17{rcub}{dollar}N{dollar}sb{lcub}rm x{rcub}{dollar} and Sm{dollar}sb2{dollar}Fe{dollar}sb{lcub}17{rcub}{dollar}C{dollar}sb{lcub}rm x{rcub}{dollar} where atoms are placed in the interstitial positions located near rare earth sites.