Huge influence of hydrogenation on the magnetic properties and structures of the ternary silicide NdMnSi

Abstract

International audienceThehydride NdMnSiH obtained by exposure of the ternary silicide NdMnSiunder a pressure of 4 MPa of hydrogen at 523K crystallizes in the tetragonal ZrCuSiAs-type structure where H atomoccupies the tetrahedral [Nd₄] sites. The hydrogenation of NdMnSi inducesan increase in the unit cell volume close to 3.3%.The investigation of NdMnSiH by magnetization and specific heat measurementsreveals the existence of two antiferromagnetic ordering, respectively, at <i>T</i>_<i>N</i>1=565(5) Kand <i>T</i>_<i>N</i>2=103(4) K. Neutron powder diffraction shows that these Néel temperaturesare associated with an antiferromagnetic arrangement of the (i) Mnsubstructure (<i>T</i>_<i>N</i>1) and (ii) Nd substructure linked to a reorientationof the Mn one (<i>T</i>_<i>N</i>2). Comparison of the <i>T</i>_<i>N</i>1 and<i>T</i>_<i>N</i>2 temperatures of NdMnSiH to those reported for the initialcompound NdMnSi indicates a strong increase in <i>T</i>_<i>N</i>1 (280 K -> 565 K)and a significant decrease in <i>T</i>_<i>N</i>2 (185 K -> 03 K). The magnetic properties, magnetic structures, and values of Nd and Mn ordered magnetic moments are discussed using both band structure calculations and comparison with the behaviors of other ternary silicides and germanides based on manganese and rare earth elements

Hydrogenation studies on NdScSi and NdScGe

“…This result is very similar to that observed previously for CeScGe [16], GdScGe [17] or GdTiGe for which hydrogen insertion completely destroys the long range ferromagnetic order [45]. Density Functional Theory (DFT) calculations would be helpful to explain such a change in the magnetic properties, notably to determine the role of the electronic effect of H-atom insertion versus that of volume cell expansion.…”

“…This may be related to the larger size of the germanium atom with respect to the silicon one in addition to the repulsive interaction between the H and X atoms (X¼Si, Ge). Such repulsive interactions have already been reported, for example, in La 3 Pd 5 SiD x deuterides [33] or in RETXHh y d r i d e s( RE¼rare earth, T¼transition metal) in which strong displacements of Si atoms are observed upon hydrogenation [34][35][36].…”

“…This suggested the existence of probably more than one interstitial site for hydrogen and/or the existence of a homogeneity range. Indeed, in the case of CeFeSi-type intermetallics, hydrogenation leads to stoichiometric ZrCuSiAs-type hydrides with only one site, the Ce 4/4 tetrahedra, fully occupied by hydrogen [34][35][36][37]. As a result, we The values marked with " n " correspond to U iso parameters whereas the values without " n " correspond to U eq parameters.…”

“…The hydrogen insertion has a drastic influence on the magnetic ground state. Recent examples are the pairs CeScSi/CeScSiH [16] and GdScGe/GdScGeH [17].I n both cases hydrogenation leads to a drastic decrease of the magnetic ordering temperature: (i) T N decreases from 26 to 3 K from CeScSi to CeScSiH and (ii) the 350 K ferromagnet GdScGe switch to the 6 K antiferromagnet GdScGeH.…”

Review on magnetic and related properties of RTX compounds

“…The hydrogenated compound GdTiGeH shows paramagnetic nature in the temperature range of 4-300 K. The hydrogenation of NdMnSi shows a significant change in structure and magnetic properties from its parent compound [482]. The hydride adopts ZrCuSi type structure, while its parent compound…”