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Interface-Induced Magnetization and Exchange Bias in LSMO/BFO Multiferroic Heterostructures

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journal contribution
posted on 22.07.2020 by Champa Lal Prajapat, Harsh Bhatt, Yogesh Kumar, T. V. Chandrasekhar Rao, Prasant K. Mishra, Gurazada Ravikumar, Christy J. Kinane, Biswarup Satpati, Andrew Caruana, Sean Langridge, Saibal Basu, Surendra Singh
Interface-induced magnetization in BiFeO3 (BFO) at the La0.67Sr0.33MnO3 (LSMO)/BFO interface is an important factor in determining the magnetoelectric coupling, exchange bias, and other phenomena in LSMO/BFO heterostructures. Using spin-dependent polarized neutron reflectivity (PNR), we report experimental evidence for the existence of a ferromagnetic (FM) interfacial BFO layer of a relatively large thickness of ∼8–15 unit cells (u.c.) at the LSMO/BFO interface. The interfacial FM BFO layer in different LSMO/BFO heterostructures is coupled both FM and antiferromagnetically (AFM), with the FM LSMO layer at the LSMO/BFO interface. We find an enhanced magnetization of 165 emu/cc (FM coupled) to −135 emu/cc (AFM coupled) for the interfacial BFO layer. We also observed an exchange bias in LSMO/BFO heterostructures, which was independently confirmed using PNR measurements by investigating the magnetization of the system under field cooling in a magnetic field of ±500 Oe. Our results further suggest that while interface roughness favors the formation of an interfacial ferromagnetic BFO layer with a higher thickness and order temperature, strain plays an important role in increasing the exchange bias blocking temperature in the LSMO/BFO heterostructure.