Structure and magnetic properties of Nd2Co17−xGax compounds studied by magnetic measurements and neutron diffraction

Abstract

The structural properties of Nd Co \V Ga V compounds (x"5, 6 and 7) were studied by means of neutron diffraction. The refinement results of the neutron powder diffraction patterns show that the Ga atoms completely avoid the 9d site in the rhombohedral Th Zn structure. Furthermore, the Ga atoms increasingly occupy the 6c and 18f sites at the cost of the 18h site that shows a decreasing Ga occupancy in this concentration range. At 4.2 K, the easy magnetisation direction is perpendicular to the c-axis for x"5 and 6, but parallel to the c-axis for x"7. From magnetic measurements and neutron diffraction it is derived that the Co and Nd moments at 4.2 K strongly decrease with increasing Ga concentration. There is also a strong decrease of the Curie temperature with Ga increasing concentration.1998 Elsevier Science B.V. All rights reserved.

Effect of substitution of Ga on the structure and magnetic properties of Dy2Co17−xGax (0≤x≤7) compounds

“…Table II shows that the Ga atom occupies

Figure 4.(Color online) Temperature dependence of the magnetization (M-T curves) for Dy 2 Co 17− x Ga x with x =3.5, 4, 4.5, 5, 5.3, 5.6, and 6 measured in an applied field of 0.1 T and temperature range from 90 to 800 K.

the entire four crystallographic sites and has a preference to occupy the 6 c site. The results do not agree with those reported for Tb x Co 17− x Ga x (Moze et al , 1998a) and Nd 2 Tb 17− x Ga x (Moze et al , 1998b). They reported that the 9 d site was completely avoided by the Ga atoms over the entire concentration range.…”

“…On the contrary, some R 2 Co 17− x Ga x [ R =Ho (Zhang et al , 1998a), Pr (Zhang et al , 1998b), Dy (Zhang et al , 1998c, d)] compounds were reported to have easy plane anisotropy over almost the entire concentration range of investigation. Rietveld refinement results of neutron powder diffraction of Tb 2 Co 17− x Ga x and Nd 2 Co 17− x Ga x (Moze et al , 1998a, b) accounted for the spin-reorientation transition, which showed that the Ga atoms initially occupy almost exclusively the 18 h site in the rhombohedral Th 2 Zn 17 structure, but then occupy both the 6 c and 18 f sites at the cost of the 18 h site when the Ga content increases. A decrease in Ga occupancy in the 18 h site in the entire concentration range was also reported.…”

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

“…In recent years, double substitution of Fe by two elements has attracted much interest [21][22][23][24]. The investigations on the structural and magnetic properties of Al and Si disubstituted Nd 2 for Fe could result in a further enhancement in the magnetic properties compared to the corresponding single substitution [21].…”

“…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].…”