Structural and magnetic properties of RMn2-xFexD6 compounds (R=Y, Er; x ≤ 0.2) synthesized under high deuterium pressure

RMn2-xFexD6 compounds were obtained by applying a deuterium pressure of several kbar to RMn2-xFex compounds for x <= 0.2 and R=Y, Er. These compounds are isostructural to RMn2D6 compounds and crystallize in a K2PtCl6 type structure with a random substitution of R and half the Mn atoms in the same 8c site whereas the other Mn atoms are located on the 4a site and surrounded by six D atoms (24e site). According to neutron powder diffraction analysis the Fe atoms are preferentially substituted on the 4a site. YMn2-xFexD6 compounds are paramagnetic and their molar susceptibility follows a modified Curie-Weiss law. ErMn2-xFexD6 compounds display a ferromagnetic behavior at 2 K, but their saturation magnetization (M-S similar to 4.0 mu(B)/f.u.) is half that of their parent compounds (M-S similar to 8.0 mu B/f.u.). The neutron diffraction patterns of ErMn1.8Fe0.2D6 display below 13 K both ferromagnetic and antiferromagnetic short range order, which can be related to a disordered distribution of Er moments. The paramagnetic temperatures of ErMn2-xFexD6 compounds are negative and decrease versus the Fe content whereas they are positive and increase for their parent compounds. (C) 2010 Elsevier Inc. All rights reserved.