Antiferromagnetic ground state in NpCoGe

Article

关键词: HEAVY-FERMION SYSTEMS;    PHASE-TRANSITIONS;    WEAK FERROMAGNETISM;    MAGNETIC-STRUCTURES;    SUPERCONDUCTIVITY;    METALS;    URHGE;    UCOGE;    COEXISTENCE;    ALLOYS;   

DOI  :  10.1103/PhysRevB.89.115135

来源: SCIE

【 摘 要 】

NpCoGe, the neptunium analog of the ferromagnetic superconductor UCoGe, has been investigated by dc magnetization, ac susceptibility, specific heat, electrical resistivity, Hall effect, Np-237 Mossbauer spectroscopy, and local spin-density approximation (LSDA) calculations. NpCoGe exhibits an antiferromagnetic ground state with a Neel temperature T-N approximate to 13 K and an average ordered magnetic moment = 0.80 mu(B). The magnetic phase diagram has been determined and shows that the antiferromagnetic structure is destroyed by the application of a magnetic field (approximate to 3 T). The value of the isomer shift suggests a Np3+ charge state (configuration 5f(4)). A high Sommerfeld coefficient value for NpCoGe (170 mJ mol(-1) K-2) is inferred from specific heat. LSDA calculations indicate strong magnetic anisotropy and easy magnetization along the c axis. Mossbauer data and calculated exchange interactions support the possible occurrence of an elliptical spin-spiral structure in NpCoGe. The comparison with NpRhGe and uranium analogs suggests the leading role of 5f-d hybridization, the rather delocalized character of 5f electrons in NpCoGe, and the possible proximity of NpRuGe or NpFeGe to a magnetic quantum critical point.

【 授权许可】

Free