Ab initio approach of the hydrogen insertion effect on the magnetic properties of YFe2

Based on experimental crystallographic and magnetic results on the family of hydrides YFe2Hx (

Properties of ZrNi5 deuteride synthesized under high pressure studied by neutron diffraction and first principles calculations

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Study of the multipeak deuterium thermodesorption in YFe2Dx (1.3 ≤ x ≤ 4.2) by DSC, TD and in situ neutron diffraction

International audienceThe deuterium thermal desorption of various YFe2Dx (x = 1.3, 2.5, 3.5, 4.2) compounds has been studied using differential scanning calorimetry (DSC) and thermal desorption (TD) experiments. These studies show that the number of desorption peaks increases with the deuterium content. In order to understand the origin of this multipeak behaviour, in situ neutron diffraction experiments during thermal desorption have been performed from 290 K to 680 K on YFe2D4.2. Upon heating, a multipeak TD spectrum is observed. It relates to the existence of several YFe2Dx phases with different stabilities. The rate limiting step of this thermal desorption has been therefore attributed to several successive phase transformations rather than to different types of interstitial sites as proposed in previous TD models reported for C15-Laves phase compounds

Thermomagnetic conversion of low-grade waste heat into electrical power

International audienceA theoretical study relying on the thermal modelling of a Curie wheel, used for the conversion of low-grade waste heat into electrical power, is presented in this paper. It allows understanding the thermal behaviour of a Curie wheel operating in steady state in order to optimise its design. To this end, a stationary one-dimensional analytical thermal model, based on a Lagrangian approach, was developed. It allows determining the local distribution over time of the temperature in the magnetocaloric material exposed to a periodic sinusoidal heat source. Thanks to this model, the effects of different parameters (nature of the magnetocaloric material, nature and temperature of the fluid) were highlighted and studied

Structural, thermal and magnetic properties of ErMn2D6 synthesized under high deuterium pressure

A new phase of ErMn2D6 has been prepared by applying high hydrogen pressure on C14 ErMn2. This phase is isostructural to YMn2D6 and crystallizes with a K2PtCl6 type structure having an ordered anion and a partially disordered cation arrangement as Er and half the Mn atoms are randomly substituted in the same 8c site. This hydride is very stable and decomposes into ErD2 and Mn at about 630 K. The reverse susceptibility follows a Curie - Weiss law with an effective moment of 10 mu(B) similar to that of ErMn2. Although a saturation magnetization of 5 mu(B) is measured at 4.2 K, smaller than that of ErMn2 (8 mu(B)), no long range magnetic order is observed in the neutron patterns. Short range magnetic order, corresponding to both ferromagnetic and antiferromagnetic correlations, is observed in the neutron patterns up to 5 K. The chemical disorder of Er and Mn atoms on the 8c site should prevent the long range magnetic order and favour a distribution of Er spin orientation

Drastic changes in electronic, magnetic, mechanical and bonding properties from Zr2CoH5 to Mg2CoH5

Despite similarities in formulae and local structures of Zr2CoH5 and Mg2CoH5, they are shown from ab initio calculations to present contrasted electronic, magnetic, mechanical and bonding properties due to the environment of cobalt with hydrogen characterized by negatively charged CoHx entities (x=4, 5 resp.) and to the chemical nature of Zr versus Mg. Zr2CoH5 is found more cohesive, harder and less ductile than Mg2CoH5. High density of states at the Fermi level arises from out-of-plane non-bonding Co-dz2 in Zr2CoH5 which is found as metallic ferromagnet in the ground state, in contrast with non-magnetic and insulating Mg2CoH5