Magnetic transitions and the magnetocaloric effect in the Pr1-xYxMn2Ge2 system

Layered rare earth compounds in the RMn2X2 series (R = rare-earth; X = Ge, Si) are of interest for potential cooling applications at lower temperatures as they enable the structural and magnetic behavior to be controlled via substitution of R, Mn, and X atoms on the 2a, 4d, and 4e sites respectively. We continue investigations of the Pr1-xYxMn2Ge2 magnetic phase diagram as functions of both composition and Mn-Mn spacing using X-ray and neutron diffraction, magnetization and differential scanning calorimetry measurements. Pr1-xYxMn2Ge2 exhibits an extended region of re-entrant ferromagnetism around x ∝ 0.5 with re-entrant ferromagnetism at TcPr ∝ 50 K for Pr0.5Y0.5Mn2Ge2. The entropy values -ΔSM around the ferromagnetic transition temperatures TCinter from the layered antiferromagnetic AFl structure to the canted ferromagnetic structure Fmc (typically TCinter ∝ 330-340 K) have been derived for Pr1-xYxMn2Ge2 with x = 0.0, 0.2, and 0.5 for ΔB = 0-5 T. The changes in magnetic states due to Y substitution for Pr are discussed in terms of chemical pressure, external pressure, and electronic effects. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)