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Pressure effect on resistivity of U2Ni2Sn

Úterý, 11.02.2020 15:00

Přednášející: I. Halevy (Department of Physics, IAEC-NRCN, Beer-Sheva, Israel)
Místo: Seminar room No. 117
Pořadatelé: Oddělení teorie kondenzovaných látek
Abstract: Electric resistivity of the U2Ni2Sn single crystal have been studied under pressures up to 3.3 GPa in order to establish the evolution of the magnetic interactions in this compound. Since U2Ni2Sn is the uniaxial antiferromagnet (TN = 25 K) with the pronounced anisotropy indicated by the anisotropy field well above 60 T, the measurements have been performed with the electric current both along and perpendicular to the easy magnetization axis, which is the [001] direction in U2Ni2Sn [1]. The resistivity curves for both current orientations are similar in shape and magnitude, the ρ(T) for i // [110] running somewhat higher (Figure 1). The shape of the resistivity curves and relatively low residual resistivity excluding the effect of the structural disorder point to the scattering of the conduction electron on spin fluctuations. The bump around 25 K is associated with the AFM ordering.
The low-temperature resistivity can be approximated by the sum of the Fermi-liquid AT2 and magnon (B*T)*exp(-Δ/T) terms, where A and B are constants and Δ represents the excitation gap. The application of the hydrostatic pressure increasing from the ambient value till 3.3 GPa results in the monotonous increase of the excitation gap Δ from about 30 K to 50 K. The Δ values for the i // [110] geometry are consistently higher than for i // [001] by about 15%, yet the shapes of the Δ(p) dependences are similar for both current directions. This difference increases further, due to the decrease of Δ for i // [001], if the magnetic field is applied. The gaps for the other geometry remain unchanged. The Néel temperature at first increases with the increasing pressure till p = 3 GPa but then drops down upon further pressurization.
The absence of the low-laying magnetic excitations as well as anisotropic field effect on the effective spin gap are consistent with the uniaxial anisotropy of the magnetic structure of U2Ni2Sn.
[1] S. Mašková et al., Phys. Rev. B 99 (2019) 064415.

Figure 1. Zero-field resistivity of U2Ni2Sn for the different electric current directions. The inset shows the transition region