Antiferromagnetic Kondo lattice NpNi${}_2$Sn

The compound NpNi${}_2$Sn has been studied by means of x-ray diffraction, heat capacity, magnetic and electrical transport measurements performed over a wide range of temperatures and applied magnetic fields. The results revealed Kondo-lattice behavior and antiferromagnetic ordering below the Néel temperature of 13 K. The compound has been characterized as a moderately enhanced heavy-fermion system, one of very few known amidst Np-based intermetallics.

Figure 1

Temperature dependence of the reciprocal molar magnetic susceptibility of NpNi${}_2$Sn measured in a field of 7 T. The solid line represents the fit of the modified Curie-Weiss law with the parameters given in the text. The upper inset presents the magnetic-field variation of the magnetization measured at a fixed temperature of 2 K. The lower inset displays the low-temperature magnetic-susceptibility data (left axis) and the temperature derivative of the $\chi T$ product (right axis).

Figure 2

Heat capacity over temperature ratio of NpNi${}_2$Sn as a function of squared temperature. The solid line represents the fit of Eq. (1) to the experimental data. The left inset shows the temperature dependence of the heat capacity up to 300 K. The right inset displays the specific heat over temperature ratio near the Néel temperature measured in various magnetic fields.

Figure 3

Temperature dependence of the electrical resistivity of NpNi${}_2$Sn, measured in a zero magnetic field and in a magnetic field of 9 T. The solid line denotes the logarithmic dependence in the paramagnetic state. The inset presents the temperature derivative of the resistivity at 0 and 9 T.

Figure 4

Temperature dependence of the Hall coefficient of NpNi${}_2$Sn, measured in a field of 14 T. The inset presents the $R_H$ vs $\rho {\chi }^{*}$ dependence. The solid line denotes the fit of Eq. (4) to the experimental data.

Figure 5

Temperature dependence of the thermoelectric power of NpNi${}_2$Sn. The solid line is the fit of Eq. (7) to the experimental data. The inset presents the low-temperature data. The arrow marks the magnetic phase transition.

Figure 6

${}^{237}$Np Mössbauer spectra of NpNi${}_2$Sn recorded at 25 K and 4.2 K.