Structural and magnetic properties of R(Fe1−yCoy)12−xNbx compounds

Abstract

The magnetic properties of RFe12−xNbx and R(Fe1−yCoy)11.3Nb0.7 compounds with R=Y, Tb, and Dy have been investigated in the concentration region defined by 0.6<x<0.8 and y⩽0.3, where the compounds are single phase with the ThMn12-type of structure. The Curie temperature TC of the RFe12−xNbx compounds is almost independent of the Nb content whereas the saturation magnetization Ms decreases with increasing Nb content. The spin-reorientation temperature Tsr of the TbFe12−xNbx and DyFe12−xNbx compounds decreases monotonically with increasing x. Substitution of Co for Fe in RFe11.3Nb0.7 leads to a remarkable increase of TC and the appearance of a maximum in the Co-concentration dependence of Ms. In contrast, Tsr decreases monotonically with increasing Co content for both R=Tb and Dy. The modification of T- and R-sublattice anisotropy originating from a change of the Nb content and from substitution of Co for Fe was analyzed by combining crystalline electric field theory and the individual-site model.

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

“…As shown in Figure 1, the lattice parameters increase slightly with increasing Ta content, consistent with the larger radius of Ta compared with Fe and similar to the behaviour of HoFe 12jx Ta x [4]. We also find that the Ta atoms occupy only the 8i sites in all of the compounds; this can be understood in terms of enthalpy effects and metallic radii as for the RFe 12jx Nb x system [6].…”

“…Below room temperature, two anomalies (marked by arrows in Figure 2a) are detected in the #-T curves. 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 .…”

“…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]. In order to clarify the question of the compositional dependence of the magnetocrystalline anisotropy in the RFe 12jx Ta x system, we have investigated the structural and magnetic properties of DyFe 12jx Ta x (x = 0.5, 0.6, 0.65 and 0.7).…”

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

“…Besides, concerning the nature of the 8f type occupation, the enthalpy effects reinforce the site preference due to the size effect. This agrees with the conclusion of a recent investigation made on Nb substituted compounds [8]. The X = H, C, N light elements are known to accommodate octahedral interstitial sites in many intermetallic systems.…”

Investigations on the structural and magnetic properties of doubly substituted Nd2Fe17−x−yTixGay compounds (0≤x≤1.0, 0≤y≤3)

“…Since the Nd-Fe-B permanent magnets with high performance were discovered many efforts have been made to explore novel rare earth-transition metal (R-T) intermetallic compounds and investigate their intrinsic magnetic properties [1][2][3][4][5][6][7]. Among the novel R-T intermetallic compounds, R 2 Fe 17 intermetallic compounds possess higher magnetization and have been receiving considerable attentions for their potential applications as permanent magnets [8][9][10].…”