Strain release versus recrystallization in magnetoelectric arrays of embedded ferrite nanostructures

Artificial multiferroic heterostructures are of high interest in many fields especially for their expected high industrial impact. We undertook a long-term project aiming at determining the coupling phenomena between the strain state, magnetic properties and ferroelectric properties in multiferroic composites made of embedded MFe2O4 ferrites (MFO, M = Co, Ni, Mn and Fe) in prototypical epitaxial BaTiO3 (001) (BTO) layers. Recrystallization by air annealing of the micron sized platelets is required to obtain long range magnetic and ferroelectric orderings which does not lead to intermixing because spinels and perovskites are phase separation systems. Importantly, multiferroicity may be lost when the interface lattice clamping is released, a compromise in annealing temperature needs thus to be found. We intend here to determine the local strain release within embedded platelets upon recrystallization by scanning X-ray microdiffraction.