Specific heat of the antiferro/ferro-magnet NpGa3

Research highlights: → The Actinide Research Department at ITU is devoted to basic and strategic research on actinide elements and compounds. The scientific programme encompasses both physics and chemistry, and is carried out in collaboration with a number of academic research partners worldwide. → The availability of state-of-the-art instrumentation adapted for measuring spectroscopic, thermodynamic and transport properties of radioactive samples, together with specialised facilities for preparation and characterisation of high quality samples, makes the department a centre of excellence in actinide research and one of the leading institutions in this field. → The object of actinide research is the understanding of chemical bonding in, and the solid-state physics properties of, the actinide metals and their compounds. The level of knowledge of actinides is far inferior to that of the rest of the periodic table, mainly because of the difficulty of handling transuranium materials, but also because of the inherent difficulty of understanding the behavior of the 5f-electrons. Their spatial extent and tendency to interact with electrons on ligand sites give actinide elements a complexity unique in the periodic table. Experiments and theory are performed with a view to improved understanding. - Abstract: The specific heat of NpGa3 has been measured for the first time. The magnetic transitions and more generally the full magnetic phase diagram have been re-established precisely. The Sommerfeld coefficient and the magnetic entropy point to a rather localized system, in agreement with previous studies, in particular high pressure Moessbauer and resistivity. The comparison with other NpX3 suggests that NpGa3 is the most localized member of the series.