Influence of high pressure on the remarkable itinerant electron behaviour in Y$_{0.7}$Er$_{0.3}$Fe$_2$D$_{4.2}$ compounds

Abstract

Monoclinic Y$_{0.7}$Er$_{0.3}$Fe$_2$D$_{4.2}$ compound exhibits unusual magnetic properties with different field induced magnetic transitions. The deuteride is ferrimagnetic at low temperature and the Er and Fe sublattices present magnetic transitions at different temperatures. The Er moments are ordered below T$_{Er}$=55 K, whereas the Fe moments remain ferromagnetically coupled up to T$_{M0}$ = 66 K. At T$_{M0}$ the Fe moments display a sharp ferromagnetic-antiferromagnetic transition (FM-AFM) through an itinerant electron metamagnetic (IEM) behaviour very sensitive to any volume change. Y$_{0.7}$Er$_{0.3}$Fe$_2$D$_{4.2}$ becomes paramagnetic above T$_N$=125 K. The pressure dependence of T$_{Er}$ and T$_{M0}$ have been extracted from magnetic measurements under hydrostatic pressure up to 0.49 GPa. Both temperatures decrease linearly upon applied pressure with dT$_{Er}$/dP=-126 and dTM0/dP=-140 K.GPa$^{-1}$ for a field of B=0.03 T. Both magnetic Er and ferromagnetic Fe order disappear at P=0.44(4) GPa. However, under a larger applied field B=5 T, dT$_{M0}$/dP=-156 K.GPa$^{-1}$ whereas dT$_{Er}$/dP=-134 K.GPa$^{-1}$ showing a weaker sensitivity to pressure and magnetic field. At 2 K the decrease of the saturation magnetization under pressure can be attributed to a reduction of the mean Er moment due to canting and/or crystal field effect. Above T$_{M0}$ the magnetization curves display a metamagnetic behaviour from AFM to FM state, which is also very sensitive to the applied pressure. The transition field B$_{trans}$, which increases linearly upon heating, is shifted to lower temperature upon applied pressure with dT=-17 K between 0 and 0.11 GPa. These results show a strong decoupling of the Er and Fe magnetic sublattices versus temperature, applied field and pressure.