5TH International Congress on Technology - Engineering & Science - Kuala Lumpur - Malaysia (2018-02-01)

Strain Effects And Symmetry Mismatch At Heterointerfaces In Bifeo3/lafeo3 Superlattices

Bismuth ferrite (BiFeO3 or BFO) is the most studied multiferroic due to its robust ferroelectric state coexisting at room temperature with an antiferromagnetic order. Such coexistence and the possible cross coupling between both ferroic orders pave the way to so-called MagnetoElectric RAM combining advantages of the ferroelectric and the antiferromagnetic state. Similarly to the relaxor-ferroelectric systems a morphotropic phase boundary has been observed in La doped BFO (Bi,La)FeO3 solid solution with peculiar nanoscale mixture. Emergence of such MPB is believed to arise from the competition between antiferrodistortive and ferroelectric instabilities. Our approach to investigate the structural interaction between BFO and LFO is based on superlattices that are ideal platforms for exploring antagonistic interactions at the origin of many exotic systems. For instance Cuprates combined with Manganites in superlattices were investigated to better understand the competition between magnetic and superconducting orders. Similarly to this strategy we grew series of SLs made of BiFeO3 and LaFeO3. Structural characterizations and Raman spectroscopy indicate an anti-polar structure in the BFO layers that is strongly dependent on the BFO thickness and temperature [1]. This antiferroelectric like structure very similar to the PbZrO3 system cannot be explained by the nature of the induced strain but by the symmetry mismatch at the interfaces of the SLs. Compatibility of the octahedral tilt system seems to be the main driving force for this induced anti-polar state. Thickness-temperature phase diagram is constructed. [1] B. Carcan et al., Adv. Mater. Interfaces, 4, 1601036 (2017)
Benjamin Carcan, Houssny Bouyanfif, Mimoun El Marssi, Françoise Le Marrec, Louic Dupont, C Davoisne