Anomalous effects of Sc substitution and processing on magnetism and structure of (Gd_(1-x)Sc_x)_5Ge_4

摘要

The kinetic arrest observed in the parent Gd5Ge4 gradually vanishes when a small fraction (x = 0.025, 0.05 and 0.10) of Gd is replaced by Sc in (Gd1-xScx)(5)Ge-4, and the magnetic ground state changes from antiferromagnetic (AFM) to ferromagnetic (FM). A first order phase transition coupled with the FM-AFM transition occurs at T-C = 41 K for x = 0.05 and at T-C = 53 K for x = 0.10 during heating in applied magnetic field of 1 kOe, and the thermal hysteresis is near 10 K. The first-order magnetic transition is coupled with the structural Sm5Ge4-type to Gd5Si4-type transformation. The magnetization measured as a function of applied magnetic field shows sharp metamagnetic-like behavior. At the same time, the AFM to paramagnetic transition in (Gd1-xScx)(5)Ge-4 with x = 0.10, is uncharacteristically broad indicating development of strong short-range AFM correlations above the Ned temperature. Comparison of the magnetization data of bulk, powdered, and metal-varnish composite samples of (Gd0.95Sc0.05)(5)Ge-4 shows that mechanical grinding and fabrication of a composite have little effect on the temperature of the first-order transformation, but short-range ordering and AFM/FM ratio below T-C are surprisingly strongly affected.