Neutron powder diffraction study of the RFe_11.5Ta_0.5(RequivLu, Er, Ho, Dy and Tb) compounds

Abstract

We report a systematic study of the crystallographic and magnetic structures of the RFe11.5 Ta0.5 (R Lu, Er, Ho, Dy and Tb) compounds carried out by means of neutron powder diffraction. Thermal dependencies of lattice parameters, magnetic moments and magnetization directions have been determined. The hierarchy of the Fe magnetic moments at the 8i, 8j and 8f sites was found to be µ8i >µ8j µ8f for all compounds at all temperatures. The influence of the atomic environments on the strength of the Fe local moments at each of the crystallographic sites is discussed. The results of the magnetic refinement are compared to those previously obtained from magnetic measurements on the same compounds.

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

“…Based on the similarity to DyFe 12jx T x with T = Nb [6], T = Ti [9], and T = W [10], the anomalies can be ascribed to the effects of spin reorientation. With decreasing temperature from room temperature (as confirmed by neutron powder diffraction measurement [3]), the easy magnetization direction of the DyFe 12jx Ta x compounds changes from easy axis at T sr1 , via an easy-cone range, to easy plane at T sr2 .…”

“…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].…”

Structural stability, site preference and lattice vibrations of RFe12−xTax (R = Tb, Dy, Ho)

“…The interest in having as small an amount as possible of the third element, critical for the stabilization of the iron-rich phase with ThMn 12 -type structure, lies in the avoidance of the severe decrease in the Curie temperature and iron magnetization when increasing the M metal concentration to the upper limit of its solubility range [5,6]. However, up to the present only a few RFe 12−x M x systems are known which comply with this requirement; they form for M = Ta (x ≈ 0.5-0.7) [7][8][9][10], Nb (x ≈ 0.6-0.7) [11][12][13][14][15][16], and W (x ≈ 0.7) [17]. Apparently, the compounds with the highest iron content form when M is a 4d or 5d element, and particularly, with rare earths from Tb to Ho.…”