Unusual magnetic and structural transformations of DyFe4Ge2

Abstract

Magnetization of DyFe${}_{4}$Ge${}_{2}$ measured as function of temperature in a 1 kOe magnetic field indicates antiferromagnetic (AFM) ordering at ${T}_{\mathrm{N}}$ $=$ 62 K followed by two spin reorientation transitions at ${T}_{f}$${}_{1}$ $=$ 52 and ${T}_{f}$${}_{2}$ $=$ 32 K and one unusual anomaly at 15 K (${T}_{f}$${}_{3}$). Three transitions (${T}_{f}$${}_{1}$, ${T}_{f}$${}_{2}$, and ${T}_{\mathrm{N}}$) are further confirmed by heat capacity measurement in a zero magnetic field. The two low-temperature magnetic transitions are broadened and gradually vanish when the applied magnetic field exceeds 30 kOe, and the AFM transition shifts toward low temperatures with an increasing magnetic field. The reentrant magnetic glassy state is observed below the freezing point of ${T}_{f}$${}_{3}$ $=$ 15 K. Two field-induced metamagnetic phase transitions are observed between 2 and 50 K in fields below 140 kOe. A temperature-magnetic-field phase diagram has been constructed. The first-principles electronic structure calculations show that the paramagnetic tetragonal structure of DyFe${}_{4}$Ge${}_{2}$ is stable at high temperatures. The calculations with collinear Dy spins confirm ferrimagnetic orthorhombic DyFe${}_{4}$Ge${}_{2}$ as the ground-state structure.