Strain induced ferromagnetism in epitaxial Cr2O3 thin films integrated on Si(001)

We report on the epitaxial growth and magnetic properties of antiferromagnetic and magnetoelectric (ME) Cr2O3 thin films deposited on cubic yttria stabilized zirconia (c-YSZ)/Si(001) using pulsed laser deposition. The X-ray diffraction (2ϴ and Φ) and TEM characterizations confirm that the films were grown epitaxially. The Cr2O3(0001) growth on YSZ(001) occurs with twin domains. There are four domains of Cr2O3 with in-plane rotation of 30° or 150° from each other about the [0001] growth direction. The epitaxial relation between the layers is given as [001]Si ‖ [001]YSZ ‖ [0001]Cr2O3 and [100]Si ǁ [100]YSZ ǁ [101¯0] Cr2O3 or [112¯0] Cr2O3. Though the bulk Cr2O3 is an antiferromagnetic with TN = 307 K, we found that the films exhibit ferromagnetic like hysteresis loops with high saturation and finite coercive field up to 400 K. The thickness dependent magnetizations together with oxygen annealing results suggest that the ferromagnetism (FM) is due to oxygen related defects whose concentration is controlled by strain present in the films. This FM, in addition to the intrinsic magneto-electric properties of Cr2O3, opens the door to relevant spintronics applications.