Nanoscale Control of Exchange Bias with BiFeO3 Thin Films

• Published in: Nano letters 2008-07, Vol.8 (7), p.2050-2055
• Main Authors: Martin, Lane W, Chu, Ying-Hao, Holcomb, Mikel B, Huijben, Mark, Yu, Pu, Han, Shu-Jen, Lee, Donkoun, Wang, Shan X, Ramesh, R
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electron states; Exact sciences and technology; Level splitting and interactions; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals; Physics; Spin-orbit coupling, zeeman, stark, and strain splitting, jahn-teller effect; Structure of solids and liquids; crystallography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl801391m

We demonstrate a direct correlation between the domain structure of multiferroic BiFeO3 thin films and exchange bias of Co0.9Fe0.1/BiFeO3 heterostructures. Two distinct types of interactions − an enhancement of the coercive field (exchange enhancement) and an enhancement of the coercive field combined with large shifts of the hysteresis loop (exchange bias) − have been observed in these heterostructures, which depend directly on the type and crystallography of the nanoscale (∼2 nm) domain walls in the BiFeO3 film. We show that the magnitude of the exchange bias interaction scales with the length of 109° ferroelectric domain walls in the BiFeO3 thin films which have been probed via piezoresponse force microscopy and X-ray magnetic circular dichroism.