Possible heavy fermion state of the caged cubic compound NdV₂Al₂₀

The magnetic susceptibility M/H, the magnetization M, and the specific heat C were measured for the caged cubic compound NdV₂Al₂₀ single crystal at temperatures down to 0.5 K in magnetic fields H along the three principal crystallographic axes [001], [101], and [111]. The electrical resistivity ρ was measured in the temperature range of 1.9-300 K. A ferromagnetic phase transition was observed at a Curie temperature T_C of 1.81 K. The easy direction of magnetization was the [001] direction at low fields, and changed to the [101] direction above 2 T. On cooling below 2 K at zero field, the specific heat divided by temperature, C/T, resulted in a large electronic specific heat coefficient γ of about 2 J/(K² mol). A large C/T of more than 1 J/(K² mol) remained at 9 T below 2 K. The temperature dependence of ρ showed the -ln T dependence at around 10 K. These behaviors possibly originate from a heavy fermion state.