Direct and indirect magnetocaloric effects near room temperature related to structural transitions in Y$_{0.9}$Pr$_{0.1}$Fe$_2$D$_{3.5}$ deuteride

TL;DR

This study investigates the structural and magnetic properties of a deuteride compound near room temperature, revealing magnetocaloric effects linked to structural transitions and magnetic ordering.

Contribution

It provides new insights into the magnetostrictive and magnetocaloric effects associated with structural phase transitions in YPrFeD compound.

Findings

Deuterium insertion causes a 23.5% cell volume increase.

The compound exhibits a first-order structural transition around 342 K.

Magnetic entropy changes indicate direct and reverse magnetocaloric effects.

Abstract

The structural and magnetic properties of Y$_{0.9}$Pr$_{0.1}$Fe$_2$D$_{3.5}$ deuteride have been investigated by synchrotron and neutron diffraction, magnetic measurements, and differential scanning calorimetry. Deuterium insertion induces a 23.5 % cell volume increase and a lowering of crystal symmetry compared to the cubic C15 parent compound (Fd-3m SG). The deuteride is monoclinic (P21/c SG) below 330 K and undergoes a first order transition between 330 and 350 K towards a pseudo-cubic structure (R-3m SG) with TO-D = 342(2) K. The compound is ferromagnetic, accompanied by a magnetostrictive effect below TC = 274 K. The analysis of the critical exponents indicates a second order type transition with a deviation from the isotropic 3D Heisenberg model towards the 3D XY model. This implies an easy plane of magnetization in agreement with cell parameter variation showing a planar magnetic orientation. A weak magnetic peak is even observed at the order-disorder transition with a maximum at 343 K. Magnetic entropy variations are characteristic of direct and reverse magnetocaloric effects at TC and TO-D respectively.