The magnetic behaviour in Dy1-xMmxCo2 (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5; Mm = mischmetal) compounds is reported using temperature and field dependence of magnetization (M-T and M-H respectively) measurements. A strong composition dependent irreversibility is observed in both the M-T and M-H scans below the magnetic ordering temperature (TC). A clear change of the first-order magnetic transition of DyCo2 to a second-order one in Dy0.5Mm0.5Co2 is evidenced by M-T and a series of Arrott (M2 versus H/M) plots, obtained from the M-H isotherms around TC. The variation in induced moments of the Co sublattice is estimated. It is found that the Mm substitution can only lead to a considerable reduction in the TC, saturation magnetization, and Co moment. The observed behaviour of M-T and M-H plots with increasing Mm content is discussed in detail. © 2010 IOP Publishing Ltd.

Sankaranarayanan V

Department Of Physics

Sundara Ramaprabhu

Field dependence

FIRST-ORDER MAGNETIC TRANSITION

Magnetic behaviour

Magnetic ordering temperatures

Misch metal

Second orders

Sub-lattices

Saturation magnetization

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IIT Madras

Magnetic behaviour in Dy1-xMmxCO2 compounds

Journal of Physics Condensed Matter

The influence of Mm substitution (Mm = mischmetal) on structural, transport and magnetic properties of (Dy1-xMmx)Co2 (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) alloys has been investigated by means of X-ray diffraction (XRD), temperature dependent electrical resistivity (ρ(T)), ac susceptibility (χ(T)) and thermopower (S(T)). XRD patterns show the formation of solid solutions crystallizing with cubic Laves (C15) type structure at room temperature. The pronounced discontinuities in the resistivity and thermopower at Curie temperature (TC) are explained based on the suppression of the spin-fluctuation contribution. The gradual decrease in TC and sharpness of discontinuities in ρ(T) and S(T) with increasing Mm substitution has been discussed. © 2008 Elsevier Ltd. All rights reserved.

Intermetallics

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

The influence of Mm (Mm=mischmetal) substitution and hydrogen absorption on the magnetic properties of Ho1-xMmxCo2 (x=0, 0.1, 0.2, 0.3 and 0.4) alloys have been determined through the temperature dependence of ac susceptibility and thermopower measurements. The changes in magnetic-ordering temperature of Ho1-xMmxCo2 alloys have been explained based on the dilution of the magnetic ions and weakening of 4f-3d exchange interactions. The gradual disappearance of the magnetic transition temperature upon increasing hydrogen concentration (y) has been interpreted by the lattice expansion and charge transfer between absorbed hydrogen and 3d-band of Ho1-xMmxCo2. © 2008.

Journal of Magnetism and Magnetic Materials

Magnetic properties of Ho1-xMmxCo2 (x=0, 0.1, 0.2, 0.3 and 0.4) alloys and their hydrides

The effect of hydrogen absorption-desorption on the structural properties of Laves phase Dy1-xMmxCo2 (x = 0.1, 0.3 and 0.5; Mm = mischmetal, a natural mixture of the light rare earth metals containing 50 wt% Ce, 35 wt% La, 8 wt% Pr, 5 wt% Nd and 1.5 wt% of other rare earth elements and 0.5 wt% Fe) alloys has been investigated by means of hydrogen absorption-desorption pressure-composition (PC) isotherms, kinetics of hydrogen absorption and powder x-ray diffraction (XRD). The PC isotherms and kinetics of hydrogen absorption have been studied in the pressure range 0.001-1 bar and temperature range 50-200 °C using Sieverts-type apparatus. The experimental results of the kinetic curves are interpreted using the Johnson-Mehl-Avrami (JMA) model and the reaction order and reaction rate have been determined. The α-, (α+β)- and β-phase regions have been identified from the different slope regions of the PC isotherms and first-order type kinetic plots. The dependence of the reaction rate parameter upon hydriding pressure and temperature in the (α+β)-phase region has been discussed. The effect of hydrogenation pressure, temperature and Mm concentration on the hydrogen-induced transformation from crystalline Dy1-xMm xCo2-H to amorphous Dy1-xMmxCo 2-H and decomposition into crystalline (Dy, Mm)H2 and Co have been discussed in detail. Further, the effect of dehydrogenation on the recovery of the crystalline Laves phase structure of Dy1-xMm xCo2 from its decomposed state is presented. This hydrogenation-disproportionation-desorption-recombination (HDDR) process can be conveniently used in powder metallurgy. © 2008 IOP Publishing Ltd.

Influence of hydrogen absorption-desorption on structural properties of Dy1-xMmxCo2 alloys

The structural and electrical transport properties of Ho1-x Mmx Co2 (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 Mg Cu2 -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. © 2007 American Institute of Physics.

Fulltext

Journal of Applied Physics

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

Journal of Rare Earths

Magnetocaloric effect of (Tb1–xCex)Co2 alloys in low magnetic field

Magnetic behaviour in Dy1-xMmxCo2 compounds

Journal	Journal of Physics Condensed Matter
ISSN	09538984
Open Access	No