Low-temperature magnetic and transport properties of single-crystal CeCoGe

Abstract

The low-temperature properties of single-crystal CeCoGe were investigated by specific heatC(T,H),magnetoresistivity ρ(T,H), and differential susceptibility measurementsχ(T,H). The zero-field low-temperature specific heat evolves asC = γT+βT3 = 42T+23.5T3 mJ mol−1 K−1. On comparingits γ = 42 mJ mol−1 K−1 with thatof LaCoGe (12 mJ mol−1 K−2) it is inferred that both 3d (Co) and 4f (Ce) orbitals contribute to the density of states at theFermi level. Assuming that its phonic contribution to the specific heat is similar to LaCoGe(β = 0.5 mJ mol−1 K−4), then the extra cubic term in the specific heat(23T3 mJ mol−1 K−1) must be due to magnon excitation within the antiferromagnetically ordered state,T<TN. On the other hand, the thermal evolution of the resistivity is found to be dominated bythe following scattering processes: magnon scattering operating within the ordered state atT<TN leadingto a T4 resistive contribution and a spin fluctuation process associated with the Cosubsystem giving rise to both a quadratic resistive term below 15 K and a saturatedresistive term at higher temperatures. The isothermal magnetoresistivity belowTN,ρ(T<TN,H), manifests a peak which is centered at the same critical field that appears in the magnetizationisotherms. This peak, together with the peak observed at a temperature 0.7 K belowTN, is attributed to a spin rearrangement of the AFM structure of the Ce sublattice.