Magnetic properties of the new compounds (, Dy, Ho, Er and Lu)

Abstract

A new series of compounds with the -type structure (, Dy, Ho, Er and Lu) has been synthesized and studied by x-ray diffraction, ac susceptibility and magnetization versus temperature and field measurements. The maximum Curie temperature is for the Tb compound . Spin reorientation transitions have been observed for the compounds and . A first order magnetization process has been observed at low temperature in and . The importance of the metallic radius of M in the magnetic properties of (for the same rate of M substitution) is discussed.

57Fe Mössbauer and magnetic studies of DyFe12−x Ta x compounds

“…Analysis of the X-ray diffraction patterns showed that all samples are essentially single phase and have the ThMn 12 -structure as expected; samples exhibited typically less than 4 wt.% of !-Fe and Fe 2 Ta as impurity phases, similar to earlier findings [2,4]. The data were refined by Rietveld analysis using the FULLPROF program.…”

“…Recently, Piquer et al [2,3] reported that the Ta-stabilized phase of RFe 11.5 Ta 0.5 only forms with the heavier rare-earth elements Tb, Dy, Ho, Er and Lu. Vert et al [4] found that pure singlephase samples do not form but that all samples included !-Fe and/or Fe 2 Ta as impurity phases and approximately single phase samples of RFe 12 j x Ta x were stabilised for x = 0.5-0.7 [4].…”

“…Vert et al [4] found that pure singlephase samples do not form but that all samples included !-Fe and/or Fe 2 Ta as impurity phases and approximately single phase samples of RFe 12 j x Ta x were stabilised for x = 0.5-0.7 [4]. Later, the magnetic structure of ErFe 11.5 Ta 0.5 was determined by neutron powder diffraction measurements and a spin reorientation detected from easy axis to easy cone at T sr = 40 K [2,3] or 49 K [5] with decreasing temperature.…”

“…For DyFe 11.5 Ta 0.5 , Piquer et al reported different values for T sr2 (T sr2 = 210 K in [3] and T sr2 = 185 K in [2]) -they attributed the difference to the fact that the change in the easy magnetization direction from cone to the basal plane is first-order but takes place gradually as the conical and basal phases may coexist with the volume ratio of one phase varying progressively with respect to the other as the temperature is lowered [3]. Recently it has been reported that T sr depends sensitively on composition in RFe 1jx Nb x and RFe 12jx Ti x for R = Tb and Dy whereas for ErFe 1jx Nb x it has been found that T sr remains essentially constant over the same concentration range [6,7].…”

Exchange interactions and magneto-crystalline anisotropy in RFe12−M and parent interstitial compounds

“…The Wigner-Seitz cell volumes of the 3d sites are ranged as follows: V(8i) > V(8j) > V(8f) [1] and it is clear that the size of the M atom plays an important role in the stabilisation of the ThMn 12 type of structure [2]. On the other hand an excessive enhancement of the unit cell volume due to the stabilising element will make the RFe 12−x M x effectively stable only in a narrower range of x compositions with Ti, Nb and Ta (1.46 < R M < 1.47 Å) than with other M elements (1.27 < R M < 1.39 Å) [3][4][5][6][7]. Besides, concerning the nature of the 8f type occupation, the enthalpy effects reinforce the site preference due to the size effect.…”