Thermal transport in Sr1−xCaxRuO3

Abstract

We have studied the thermal conductivity K(T,B) (6<T<250 K, 0<B<15 T) of single crystals of SrRuO3, a ferromagnet with Tc=160 K, and isostructural but paramagnetic CaRuO3, as well as the intermediate crystals (Sr, Ca)RuO3 for the purpose of probing charge carrier (Ke), phonon (Kp), and magnon (Km) excitations in these systems. The contributions of electron and phonon scattering processes to the thermal conductivities have been estimated using a Wiedemann–Franz relationship to estimate Ke and thus obtain Kp at higher temperatures. Roughly 50% of the thermal conductivity is estimated to be phononic near room temperature. Amorphous behavior is observed in the doped samples, and no break in the thermal conductivity is seen at the ferromagnetic onset. A comparison of magnetothermal conductivity and magnetoresistivity measurements at lower temperatures in SrRuO3 and CaRuO3 reveals that additional scattering mechanisms have become important. These investigations argue for the importance of phonon and magnon contributions, in addition to electronic contributions, to the magnetic behavior in Sr1−xCaxRuO3. Results will be discussed in relation to recent theoretical work on these systems and measurements on related systems.