Antiferro and ferromagnetic ordering in PrGe single crystal

The equiatomic PrGe single crystal was grown by Czochralski pulling method. The grown single crystal was found to have CrB-type orthorhombic crystal structure with the space group textit{Cmcm} (#63). Transport and magnetization data reveal large anisotropy in the electrical resistivity, magnetic susceptibility and magnetization. PrGe was found to exhibit two consecutive magnetic orderings at 44 K and 41.5 K, respectively. The magnetic susceptibility measurement along the three principal directions, in low applied fields, revealed a cusp like behaviour at 44 K while at 41.5 K a ferromagnetic like increase was observed. The hysteritic behaviour in the magnetization measurement at 1.8 K confirmed the ferromagnetic nature of PrGe at low temperatures. The heat capacity data clearly revealed the bulk nature of two magnetic transitions by the presence of two sharp peaks attaining values exceeding 40 J/K$cdot$mol at the respective temperatures. The absence of Schottky contribution in the magnetic part of heat capacity indicates a quasi-ninefold degenerate J=4 magnetic ground state in this system. The low temperature data of electrical resistivity and the magnetic part of heat capacity show an existence of gap in the spin-wave spectrum.

Anisotropic magnetic properties and superzone gap formation in CeGe single crystal

Single crystals of CeGe and its non-magnetic analogue LaGe have been grown by Czochralski method. CeGe compound crystallizes in the orthorhombic FeB-type crystal structure with the space group textit{Pnma} (#62). The anisotropic magnetic properties have been investigated on well oriented single crystals by measuring the magnetic susceptibility, electrical resistivity and heat capacity. It has been found that CeGe orders antiferromagnetically at 10.5 K. Both transport and magnetic studies have revealed large anisotropy reflecting the orthorhombic crystal structure. The magnetization measurement measured at 2 K revealed metamagnetic transitions along the [010] direction at 4.8 and 6.4 T and along [100] direction at a critical field of 10.7 T, while the magnetiztaion along [001] direction was increasing linearly without any anomaly up to a field of 16 T. From the magnetic susceptibility and the magnetization measurements it has been found that [010] direction is the easy axis of magnetization. The electrical resistivity along the three crystallographic directions exhibited an upturn at $T_{rm N}$ indicating the superzone gap formation below $T_{rm N}$ in this compound. We have performed the crystalline electric field (CEF) analysis on the magnetic susceptibility and the heat capacity data and found that the ground state is doublet and the splitting energies from the ground state to the first and second excited doublet states were estimated to be 39 and 111 K, respectively.