Temperature Dependence of Magnetic Anisotropy and Domain Wall Width Tuning in a BaTiO₃(111)/CoFeB Heterostructure

Composite multiferroics consist of two types of ferroic materials, typically a ferroelectric and ferromagnet, often coupled interfacially by strain induced by the lattice elongations in the ferroelectric. In BaTiO3 (BTO) substrates the magnitude of the strain is strongly temperature dependent, varying greatly between each of the polar crystal phases and exerting a huge influence over the properties of a coupled magnetic film. In this work we determine the temperature dependence of the strain-induced magnetoelastic anisotropy within ferromagnetic domains in a CoFeB film coupled to the ferroelectric domains from a BTO(111) substrate. Using our measurements of this anisotropy strength we then micromagnetically determine the scaling of magnetic domain wall widths as a function of temperature, demonstrating an increase of 100% across the entire range with the most significant changes occurring around the BTO phase transitions.