Magnon gap formation and charge density wave effect on thermoelectric properties in the SmNiC2 compound

Abstract

We studied the electrical, thermal, and thermoelectric properties of the polycrystalline compound of SmNiC2. The electrical resistivity and magnetization measurement show the interplay between the charge density wave at TCDW=150 K and the ferromagnetic ordering of Tc=18K. Below the ferromagnetic transition temperature, we observed the magnon gap formation of Δâ‰4.3-4.4 meV by ρ(T) and Cp(T) measurements. The charge density wave is attributed to the increase of the Seebeck coefficient resulting in the increase of the power factor S2σ. The thermal conductivity anomalously increases with increasing temperature along the whole measured temperature range, which implies the weak attribution of Umklapp phonon scattering. The thermoelectric figure of merit ZT significantly increases due to the increase of the power factor at TCDW=150K. Here we argue that the competing interaction between electron-phonon and electron-magnon couplings exhibits the unconventional behavior of electrical and thermal properties. © 2012 American Physical Society.