Spin Seebeck Effect in Layered Ferromagnetic Insulators CrSiTe₃ and CrGeTe₃

We have studied the longitudinal spin Seebeck effect (LSSE) in the layered ferromagnetic insulators CrSiTe₃ and CrGeTe₃ covered by Pt films in the measurement configuration where spin current traverses the ferromagnetic Cr layers. The LSSE response is clearly observed in the ferromagnetic phase and—in contrast to a standard LSSE magnet Y₃Fe₅O₁₂—persists above the critical temper- atures in both CrSiTe₃/Pt and CrGeTe₃/Pt samples. With the help of a numerical calculation, we attribute the LSSE signals observed in the paramagnetic regime to exchange-dominated interlayer transport of in-plane paramagnetic moments reinforced by short-range ferromagnetic correlations and strong Zeeman effects.