Competing Magnetic Interactions in the Kramers Doublet System NdIr2Zn20

Abstract

Electrical resistivity ρ, magnetization M, and specific heat C measurements are reported for single-crystalline samples of the 4f3 Kramers system NdIr2Zn20. On cooling, ρ(T) monotonically decreases and drops below 0.65 K. The magnetic susceptibility M/B follows the Curie–Weiss law from 300 to 20 K, leading to an effective magnetic moment of μeff = 3.59 μB/Nd and a paramagnetic Curie temperature of θp = −3.6 K. The negative value of θp indicates an antiferro-type interaction, although the enhancement of M(B) in the paramagnetic state implies a ferro-type one. A broad maximum in the magnetic specific heat Cm at around 15 K arises from the excitations from the crystalline electric field ground state of a magnetic Γ6 doublet to the excited Γ8 quartet lying at 39 K above the ground state. A sharp peak in C(T) at 0.65 K coincides with the drop in ρ(T), both of which shift to lower temperatures upon applying a magnetic field. The field dependences indicate that an antiferromagnetic order may occur under the geom...