Magnetic and Electronic Properties of NpCo2: Evidence for Long-Range Magnetic Order

The magnetic and electronic properties of the cubic Laves phase intermetallic compound NpCo2 have been investigated by magnetization, specific heat, and electrical resistivity measurements. Magnetization data confirm previous results, i.e., an antiferromagneticlike order at 12.5 K and a metamagnetic transition at Bm ∼ 4.3 T at 3 K with a saturation moment of ∼0.6 μB. Although extensive neutron diffraction studies failed to establish the nature of the antiferromagnetic order, its occurrence is confirmed by specific heat measurements that also highlight the presence of magnetic fluctuations suppressed by the application of an external field larger than Bm. The observed high value of the electronic specific heat, γ0 ∼ 330 mJ/molK2 as T → 0, and the minute magnetic entropy,