In-Situ Measurement of Magnetoelectric Coupling and Strain Transfer in Multiferroic Nanocomposites of CoFe 2 O 4 and Hf 0.5 Zr 0.5 O 2 with Residual Porosity.

With increasing applications for voltage-controlled magnetism, the need to more fully understand magnetoelectric coupling and strain transfer in nanostructured multiferroic composites has also increased. Here, multiferroic nanocomposites were synthesized using block copolymer templating to create mesoporous cobalt ferrite (CFO), followed by partly filling the pores with ferroelectric zirconium-substituted hafnia (HZO) using atomic layer deposition (ALD) to produce a porous multiferroic composite with enhanced mechanical flexibility. Upon electrical poling of the nanocomposite, we observed large changes in the magnetization. These changes partly relaxed upon removing the electric field, suggesting a strain-mediated mechanism. Both the anisotropic strain transfer from HZO to CFO and the strain relaxation after the field was removed were confirmed using high-resolution X-ray diffraction measurements collected during poling. The observation of both anisotropic strain transfer and large magnetization changes allows us to directly characterize the strong multiferroic coupling that can occur in flexible, nanostructured composites.