Specific heat study of NpX (XS, Se, Te) compounds

Abstract The specific heat measurements confirm antiferromagnetic order in NpS, NpSe and NpTe below 23, 36.5 and 45 K, respectively. The electronic specific-heat coefficient is rather enhanced in NpSe and NpTe (∼120 mJ mol −1  K −2 ) whereas it is moderate in NpS (39 mJ mol −1  K −2 ). The estimated magnetic entropy in NpS and NpSe lies well below R ln 2, indicating the delocalized character of the Np 5f states.