Anomalous Hall effect in Platinum/Nickel-Cobaltite bilayer.

Spin structure of materials plays important roles in their transport properties. In order to study whether the spin interaction at the interface between ferrimagnetic NiCo2O4 (NCO) and strongly spin-orbit coupled metal Platinum (Pt) generates novel spin structure, we prepared Pt/NCO bilayer structures on MgAl2O4 (001) substrates using pulsed laser deposition (PLD) and studied the spin transport properties at various temperature with different NCO thickness. In addition to the anomalous Hall effect expected from NCO, we observed asymmetric topological-Hall-like effects (humps). The magnitude of the humps and the magnetic field where the humps appear change dramatically with temperature, which is correlated with the coercive field of NCO. These results suggest complex spin interactions at the NCO/Pt interface which may give rise to topological spin texture.

Acknowledgment: This research was primarily supported by US DOE (DE-SC0019173).