Structural and magnetic properties of RFe2H5 hydrides (R=Y, Er)

Pressure Dependence of Hydrogen-Induced Transformations in C15 Laves Phase DyCo<SUB>2</SUB>

“…On the other hand, it has been known that intermetallic compounds A x B 1Àx with the C15, B8 2 , C23, D0 19 and L1 2 structures amorphize by hydrogenation, [1][2][3][4][5][6][7][8][9][10][11][12][13][14] which is called hydrogen-induced amorphization (HIA). HIA is a practically important phenomenon, because it is closely related to the disproportional reaction that determines the lifetime of hydrogen storage alloys.…”

Influence of doping elements (Y, Fe, V) on magnetic properties of RM2(R = Gd, Er; M = Fe, Co, Ni) Laves phases and their hydrides

“…associated with a weakening of the Er-Fe exchange interaction. This has been studied extensively in ErFe 2 H x [22][23][24]28] where the compensation point of the parent compound at 410 K linearly decreases with the hydrogen content to 170 K for ErFe 2 H 2.97 [29]. Also for ErFe 1.85 V 0.15 H 3.9 a compensation point occurs at about 80 K which is shifted to higher temperatures with rising fields but long range order remains above room temperature which is in line with the literature data mentioned above.…”

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

“…The Fe moment increases with the H content, from 1.8 B for x = 0 to 2.2 B for x = 3.5 [5,39]. For x = 4.2, a transition from a ferromagnetic to a metamagnetic state, with a magnetovolumic effect, is observed around 90 K. For x = 5, the orthorhombic hydride shows a weak magnetization (0.4 B /Fe), which is almost temperature independent [3]. The increase of the Fe moment for x ≤ 3.5 is in agreement with band structure calculations, due to the cell volume enlargement [41].…”

“…Below T S , the crystal symmetry is lowered due to the ordering of hydrogen atoms, which induces a displacement of the Y and Fe atoms [36,39]. The crystal structure below T S is related to the H content: tetragonal or cubic superstructure for 1.2 ≤ x ≤ 1.9 [36], rhombohedral for 3.3 ≤ x ≤ 4.2 [5,37], orthorhombic for x = 5 [3] (Fig. 4).…”

“…In the RM 2 Laves phases with M = Mn or Fe, the hydrogen content can be varied continuously or by steps until 5 H/f.u. leading to a cell volume increase of up to 30%, generally accompanied by a lowering of the crystal symmetry below a critical temperature [2,3]. Hydrogen absorption is therefore a way to continuously monitor the magnetic interactions, which are very sensitive to the change of the interatomic distances [4,5].…”