A study of the ferromagnetic behavior of Nd₁₆Co_76–xRu_xB₈ alloys

Abstract

The structural and magnetic properties of the tetragonal 2 : 14 : 1 hard magnetic phase (φ) were investigated in Nd 16 Co 76-x Ru x B 8 alloys. The results indicated that Ru substitution does not harm the formation of φ in Co-rich alloys. An antiferromagnetic Co -Ru coupling is concluded. The cell volume initially decreases with the Ru substitution. The coercivity is enhanced and reaches a maximum at the composition where the saturation magnetization has the lowest value. The Curie temperature as well as the mean magnetic moment decrease with increasing Ru concentration. With the increase of the Ru concentration the unit-cell volume increases. A ferrimagnetic ordering is predicted at higher Ru concentrations.

An investigation of structural and magnetic properties of the Nd16Co72-xRu xC11B coro-carbides

“…This leads to a decreasing c/a ratio as well as to a decreasing unit cell volume, with the Co substitution by Ru. This behavior differs from that observed in the Co-based borides, where the cell volume increases as Ru substitutes for Co [29]. In Fig.…”

“…Nevertheless, a residual magnetization still is seen at higher temperatures, and the collapse of the total magnetiza- tion takes place only at about 1068 K. This contribution is expected to be arising from the minority phases, as has been revealed from the X-ray diffraction studies. It is noteworthy that the Curie temperature T C of Nd 2 Fe 14 C is 535 K, while for the Co-based boride with x = 6, T C = 789 K [29]. Despite the larger unit cell volume of the tetragonal phase for x = 6, as shown in Table 1, the Curie temperature is even higher than that of the carbide with the same amount of Ru and higher Co content.…”

“…The same behavior is expected for the magnetic moment per formula unit. Hence, a conclusion which is withdrawn from the observed trends is that a composition dependence of the Ru moment might be considered as well as the development of antiferromagnetic spin correlations at higher Ru contents, as has been observed in similar compounds [26,27,[29][30][31][32]. Figure 3 shows the magnetization versus temperature curves of the Nd 16 Co 72−x Ru x C 11 B alloys registered with a magnetobalance above room temperature in a measuring field of ≈ 0.5 T. The so obtained T C values are listed in Table 1.…”

Characterization of the structural and magnetic properties of Nd16Co76-xRu xC7B alloys

“…The lattice expansion in the basal plane thus indicates that Ru preferentially occupies the Co sites, whereas the shrink of the lattice along the c direction indicates an enhanced cohesion. However, as compared to the Nd 2 (Fe 1−x Co x ) 14 B boride, the lattice contraction in the basal plane is lesser in this case [27].…”

“…As one sees, T C decreases steadly with the increase of the Ru concentration. The Curie temperatures of these alloys are lower than those of pure borides [24,27] as well as those of Nd 2 Fe 14−x Ru x B alloys [24,29]. T C is mainly determined by the direct exchange interaction of the 3d magnetic ions, and thus it is expected to change very sensitively with the increase of the Ru concentration.…”