P. Gaczyński | Searcharxiv

arXiv2018

On the magnetic and electronic properties of NpPdSn

We have studied NpPdSn by means of the heat capacity, electrical resistivity, Seebeck and Hall effect, $^{237}$Np Mössbauer spectroscopy, and neutron diffraction measurements in the temperature range 2-300 K and under magnetic fields up to 14 T. NpPdSn orders antiferromagnetically below the Néel temperature $T_N$ = 19 K and shows localized magnetism of Np$^{3+}$ ion with a a doubly degenerate ground state. In the magnetic state the electrical resistivity and heat capacity are characterized by electron-magnon scattering with spin-waves spectrum typical of anisotropic antiferromagnets. An enhanced Sommerfeld coefficient and typical behavior of magnetorestistivity, Seebeck and Hall coefficients are all characteristic of systems with strong electronic correlations. The low temperature antiferromagnetic state of NpPdSn is verified by neutron diffraction and $^{237}$Np Mössbauer spectroscopy and possible magnetic structures are discussed.

cond-mat.str-el↗

arXiv2014

Antiferromagnetic ground state in NpCoGe

NpCoGe, the neptunium analogue of the ferromagnetic superconductor UCoGe, has been investigated by dc-magnetization, ac-susceptibility, specific heat, electrical resistivity, Hall effect, 237Np Moessbauer spectroscopy and LSDA calculations. NpCoGe exhibits an antiferromagnetic ground state with a Neel temperature TN = 13 K and an average ordered magnetic moment = 0.80 mB. The magnetic phase diagram has been determined and shows that the antiferromagnetic structure is destroyed by the application of a magnetic field (around 3 T). The value of the isomer shift suggests a Np3+ charge state (configuration 5f4). A high Sommerfeld coefficient value for NpCoGe (170 mJ mol-1K-2) is inferred from specific heat. LSDA calculations indicate strong magnetic anisotropy and easy magnetization along the c-axis. Moessbauer data and calculated exchange interactions support the possible occurrence of an elliptical spin spiral structure in NpCoGe. The comparison with NpRhGe and uranium analogues 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.

cond-mat.str-el↗