Influence of Cr₂O₃ thickness on the magnetic properties of NiFe/Cr₂O₃ bilayers deposited on SrTiO₃ single-crystalline substrate

The exchange-coupled bilayers containing antiferromagnetic (AF) Cr₂O₃ have potential applications in novel spintronic devices with magneto-electric properties. The microstructures and magnetic properties of ion-beam sputtered NiFe/Cr₂O₃ bilayers are comparatively investigated at different Cr₂O₃ thicknesses on single-crystalline SrTiO₃ (STO) (001) and amorphous SiO₂ substrates. The formation of Cr₂O₃ is verified by X-ray photoelectron spectrometry. X-ray diffraction reveals a distinction in the preferred orientation of Cr₂O₃ deposited on different substrates. The variations in microstructure are responsible for the higher exchange bias, larger coercivity, and higher temperature stability of magnetization for samples grown on STO substrates. The coercivity and exchange bias at 10 K increases with Cr₂O₃ thickness. Higher Cr₂O₃ thickness also results in higher surface roughness, higher irreversibility temperature, and increased peak temperature of the out-of-phase AC susceptibility. This work has revealed the thickness dependence of the microstructure and magnetic properties of NiFe/Cr₂O₃ bilayers prepared on STO substrate. The outcome of this work may provide some insight for developing novel spintronic devices containing Cr₂O₃ and perovskite oxides.