Pressure-induced changes in the structural and magnetic properties of YFe2D4.2

Abstract

The study of the structural and magnetic properties of YFe${}_{2}$D${}_{4.2}$ under high pressure has been performed by combining energy dispersive x-ray diffraction at room temperature up to 5.5 GPa, neutron diffraction studies at low temperature up to 2.5 GPa, and magnetization measurements up to 1 GPa. The monoclinic structure of YFe${}_{2}$D${}_{4.2}$ at ambient temperature and pressure is related to a distortion of the initial cubic C15 structure of YFe${}_{2}$ by the ordering of inserted D atoms. A structural transition from monoclinic to cubic structure is observed at 4 GPa. The high pressure cubic YFe${}_{2}$D${}_{4.2}$ has a 19% higher cell volume than that of YFe${}_{2}$. The application of an external pressure leads to the progressive decrease of the transition temperature ${T}_{M}$${}_{0}$ from ferro to antiferromagnetic order (${T}_{M}$${}_{0}$ $=$ 84 K at ambient pressure) and even to the suppression of the ferromagnetic ground state for pressures larger than 0.54 GPa. Moreover using the compressibility value determined by x-ray diffraction (\ensuremath{\kappa} $=$ 0.013 GPa${}^{\ensuremath{-}1}$), the decrease of volume at the critical pressure of 0.54 GPa (0.70%) is in very good agreement with the increase of volume observed at the transition from antiferromagnetic to ferromagnetic state at ambient pressure (0.65%), indicating the crucial role of volume effect. An antiferromagnetic structure was detected between ${T}_{M}$${}_{0}$ and ${T}_{N}$ and for pressures larger than 0.54 GPa in the whole temperature range below ${T}_{N}$. In addition, a large pressure effect on the spontaneous magnetization ${M}_{S}$ for pressures below 0.4 GPa, $d$ ln ${M}_{S}$/d P $=$ \ensuremath{-}7.3 \ifmmode\times\else\texttimes\fi{} 10${}^{\ensuremath{-}2}$ GPa${}^{\ensuremath{-}1}$ was discovered. This clearly proves the delocalized character of the iron 3$d$ band magnetism in YFe${}_{2}$D${}_{4.2}$ compound. The pressure evolution of the magnetic phase diagram of YFe${}_{2}$D${}_{4.2}$ has been determined.