METALLIC HYDRIDES.Magnetic properties of laves-phase rare earth hydrides

Abstract

Neutron scattering results show that the introduction of hydrogen into RFe2 compounds (R = Tm, Ho, and Er) significantly lowers the overall Curie temperature and produces a reduced 0 K moment on the rare earth site. The rare earth spins disorder at a temperature lower than the bulk Tc in ErFe3H3.5. The 0 K iron sublattice moment in ErFe2H3.5 is essentially the same as that found in the non-hydride compounds and remains nearly constant to approximately 0.8 Tc

Comparison of the influence of hydrogen on the magnetic properties of RMn2 and RFe2 Laves phase compounds

“…The decrease of the compensation temperature observed for R = Ho, Er and Tb is attributed to the weakening of the R-Fe and R-R exchange interactions [55]. This is also confirmed by neutron diffraction experiments, showing that the ordering temperature of the R sublattice T R is lower than T C for the hydrides [42,56].…”

“…Band structure calculations are in progress to elucidate this behavior. Concerning the RFe 2 hydrides with a magnetic rare earth metal, various studies have been performed for heavy rare earth metals (Gd to Lu) [42][43][44][45]. These works indicated the existence of cubic hydrides for 1.2 ≤ x ≤ 3 and rhombohedral hydrides above 3-3.5 H/f.u.…”

“…In RFe 2 intermetallic compounds, the R moment is close to the free ion value. Neutron diffraction studies [42,50,51] indicated a fanning of almost 50% of the R moment (R = Er, Ho, Tm) for hydrides with x = 3.5. Since the observed R moment is the net projection along the Fe spin direction, this fanning has been interpreted as a distribution of the R spin orientations due to the variation of the anisotropy field by the surrounding H neighbors [50,52,53].…”

Magnetic properties of hydrogen-amorphized RCo2Hx (R=Gd, Tb, Dy, Ho, Er, Tm and Y) alloys

“…., Er determined in this way are found to be considerably lower than the values of g J J B which can be expected for rare earth compounds where exchange interactions are much stronger than crystal-field interactions. Perhaps, in these compounds a non-collinear magnetic structure with random orientations of rare earth magnetic moments is formed due to local fluctuations of crystal electric fields, similar to that for some crystalline hydrides [21] or amorphous rare earth-3d metal alloys [22].…”

Structural and magnetic properties of ErFe2D3.1

“…In the present study a careful analysis of the ErFe 2 D 3.1 NPD patterns shows the distribution of deuterium atoms over the preferential A 2 B 2 tetrahedral sites within the whole temperature range 12-450 K. In accordance with [19] the parent ErFe 2 compound exhibits week rhombohedral distortions below the Curie temperature due to magnetostriction effects. However, random magnetic anisotropy and weakened exchange interactions result in the suppression of the magnetostrictive distortions of the parent RFe 2 structure in hydride or deuteride compounds [20][21][22]. Moreover, according to our neutron diffraction data the cubic-to-orthorhombic phase transition occurs at about 400 K which is above the Curie temperature T C = 380 K. Thus we can conclude that the structure distortions of ErFe 2 D 3.1 cannot be attributed to magnetostriction properties.…”