Spin-Hall magnetoresistance and spin Seebeck effect in spin-spiral and paramagnetic phases of multiferroic CoCr2O4 films

We report on the spin-Hall magnetoresistance (SMR) and spin Seebeck effect (SSE) in multiferroic CoCr2O4 (CCO) spinel thin films with Pt contacts. We observe a large enhancement of both signals below the spin-spiral (T-s = 28 K) and the spin lock-in (Tlock-in = 14 K) transitions. The SMR and SSE responses in the spin lock-in phase are one order of magnitude larger than those observed at the ferrimagnetic transition temperature (T-c = 94 K), which indicates that the interaction between spins at the Pt vertical bar CCO interface is more efficient in the noncollinear magnetic state. At T > T-c , magnetic-field-induced SMR and SSE signals are observed, which can be explained by a high interface susceptibility. Our results show that the spin transport at the Pt vertical bar CCO interface is sensitive to the magnetic phases but cannot be explained solely by the bulk magnetization.