Influence of hydrogen absorption on structural and electrical transport properties of Ho1−xMmxCo2 alloys

Abstract

The structural and electrical transport properties of Ho1−xMmxCo2 (x=0, 0.1, 0.2, 0.3, and 0.4 and Mm=mischmetal) alloys and their hydrides in the hydrogen concentration (y) range of 0⩽y⩽3.6 have been determined through the powder x-ray diffraction (XRD) and temperature dependence of electrical resistivity [ρ(T)] measurements. At room temperature, these compounds crystallize in MgCu2-type (C15) structure. The crystalline nature and lattice expansion of hydrogenated alloys have been studied using the hydrogen concentration dependence of XRD peak analysis indicating the coexistence of two hydride phases at intermediate hydrogen concentrations. The temperature dependence of the electrical resistivity of alloys has been discussed based on the conduction electron scattering and spin fluctuation scattering mechanisms. The changes in magnetic ordering and transition temperature upon Mm substitution and at different concentrations of hydrogen loadings have been discussed. Furthermore, the transformation from metalliclike conductivity to thermally activated conduction mechanism and different conduction regimes of temperature dependent resistivity upon increasing H concentration have been well described by Kondo-type and electron-electron scattering effects.

Magnetic and transport properties of Laves phase Dy1−xMmxCo2 (x=0–0.5) alloys

“…Thus Fig. 3(b) shows the straight-line behaviour of T 2 dependent resistivity well below T C , which is attributed to the r spd [18,19]. A tendency for strong saturation in r(T), observed pertaining to the RCo 2 compounds.…”

Magnetic behaviour of hydrogenated Ho1−xMmxCo2 (x=0–0.4) alloys

“…[4]. The temperature and field dependences of magnetization measurements were performed using a SQUID magnetometer (Quantum Design, MPMS 7).…”

“…It is reported that the magnetic behaviour of HR 1−x LR x Co 2 is strongly influenced by the amount and nature of the R's. Very recently we have reported the hydrogen absorption-desorption, structure and transport properties of Mm substituted HoCo 2 , Ho 1−x Mm x Co 2 (x = 0, 0.1, 0.2, 0.3, and 0.4; Mm = mischmetal) alloys and their hydrides [4,[16][17][18]. Mischmetal is a cheap natural ore and contains the light rare earth metals: 50% Ce, 35% La, 8% Pr, 5% Nd, 1.5% other rare earth elements and 0.5% Fe.…”

“…The absorbed hydrogen very often leads to strong changes in the physical property behaviour of alloys [3][4][5]8,16,17]. In the RCo 2 series, most of the recent works have been focussed on the substitution of a rare-earth metal for one of the other magnetic lanthanides, in which the R atomic site mostly consisting of the mixture of light rare earths (LR = La, Ce, Pr, Nd, and Sm) and heavy rare earths (HR = Gd, Tb, Dy, Ho, and Er) [4,9,11,12,15]. It is reported that the magnetic behaviour of HR 1−x LR x Co 2 is strongly influenced by the amount and nature of the R's.…”

“…There has been much attention is focused on the hydrogen absorption and its influence on the electronic, magnetic and structural properties of intermetallic compounds [1][2][3][4][5][6][7][8]. Among large number of the rare earth intermetallics, magnetic RCo 2 (R = rare earth metal) Laves phase alloys have been under intense scrutiny due to their intriguing magnetic behaviour [9][10][11][12][13][14][15].…”