substrates*

The inverse spinel NiCo₂O₄ (NCO) is ferrimagnetic with high Curie temperature (T_C) and spin polarization. It is of high research interest to integrate it with other functional oxides, while many of them have the perovskite structure. We investigated the effects of a perovskite substrate on the magnetotransport properties of NCO by depositing 30 nm NCO thin films on SrTiO₃ (STO) and Sr₃Al₂O₆ (SAO) buffered STO substrates using off-axis RF magnetron sputtering. Both types of samples exhibit insulating behavior below 300 K, and the films on SAO buffered STO shows more than 10 times higher resistivity at 300 K. We estimated the T_C from the magnetoresistance hysteresis. These samples show T_C of up to 150 K, well below that for films deposited on MgAl₂O₄ substrates (above 300 K). The reduced T_C can be attributed to a high density of anti-phase boundaries due to the structural mismatch between NCO and STO. We also discuss the possibility of suspending the NCO thin films by water etching the SAO buffer layer.