A Low-T-C Superconducting Modification Of Th4h15 Synthesized Under High Pressure

Among the metal hydrides, Th4H15 is the first reported superconductor with a relatively high T-c 8 K at ambient pressure. Here we report on the synthesis and characterization of a low-T-c superconducting modification of Th4H15, which is obtained via hydrogenating Th metal at 5 GPa and 800 degrees C by using the ammonia borane as the hydrogen source. Measurements of resistivity, magnetic susceptibility, and specific heat confirm that the obtained Th4H15 sample shows a bulk superconducting transition at T-c 6 K, which is about 2 K lower than that reported previously. Various characteristic superconducting parameters have been extracted for this compound and unusual lattice dynamics were evidenced from the specific-heat analysis.