Magnetism of ordered and disordered alloys of R2Fe14B (R = Nd, Er) type

Abstract

a b s t r a c tMagnetic susceptibility, magnetization and neutron diffraction measurements have been performed to study structure and magnetic states of crystalline and amorphous Nd 2 Fe 14 B and Er 2 Fe 14 B alloys. In the crystalline state there exists a large (about 20%) anisotropy of Er-sublattice magnetization. Values of the magnetic anisotropy constant of Er ions and the Er-Fe exchange-coupling parameter were estimated using temperature dependence of the Er-and Fe-sublattice magnetizations. Amorphous state of the samples was obtained by irradiation of fast (E eff P 1 MeV) neutrons with a fluence up to the 1.2 Â 10 20 n/cm À2 at 340 K. It is shown that antiferromagnetic coupling between the rare-earth and iron spins is kept in the amorphous state. Amorphization of the samples is found to result in reduction of the Curie temperature (T C ) by about 200 K and almost total absence of coercivity. We suggest that the strong decrease of T C is a consequence of enhancement of negative Fe-Fe interactions as a result of dispersion of interatomic distances, which is a characteristic feature of the amorphous state.

2Flux growth and characterization of Ce-substituted Nd2Fe14B single crystals

“…The structure derived from the 250 K single crystal refinement is presented in Figs. 3a−3c and matches well with those published in the literature [6,7,[23][24][25].…”

Thermal expansion behavior of sintered Nd–Fe–B magnets with different Co contents and orientations

“…[12] Similarly, Ishimoto studied the fracture mechanism of radially oriented Nd-Fe-B ring magnets and attributed cracking to accumulated thermal stress resulting from the anisotropic CTE of the oriented sintered magnets during cooling. [13] Anisotropic anomalous thermal expansion in the lattices of R 2 Fe 14 B compounds has been reported in several studies, [14][15][16][17][18] with the joint action of the Fe sublattice and the R sublattice causing spontaneous magnetostriction, which is a major factor in anomalous thermal expansion. [14] Andreev studied the lattice thermal expansion of Y 2 (Fe 1−x Co x ) 14 B (x = 0, 0.1, 0.2, and 0.3) compounds and found that the Invar-type anomaly decreases with increasing of Co substitution.…”

Magnetic phase boundary of BaVS3 clarified with high-pressure μ+SR

“…that the ordered Nd moment (μ Nd ord ) is 1 μ B [38] or 1.5 μ B [39], while the neutron study using a single-crystal sample revealed that μ Nd ord = 3.2 μ B [40]. On the contrary, μ + SR on a powder sample showed that μ Nd ord = 3.31 μ B [41].…”