Oxygen-Vacancy-Induced Antiferromagnetism to Ferromagnetism Transformation in Eu0.5Ba0.5TiO3-δ Multiferroic Thin Films

Oxygen vacancies (V-O) effects on magnetic ordering in Eu0.5Ba0.5TiO3-delta (EBTO3-delta) thin films have been investigated using a combination of experimental measurements and first-principles density-functional calculations. Two kinds of EBTO3-delta thin films with different oxygen deficiency have been fabricated. A nuclear resonance backscattering spectrometry technique has been used to quantitatively measure contents of the V-O. Eu0.5Ba0.5TiO3 ceramics have been known to exhibit ferroelectric (FE) and G-type antiferromagnetic (AFM) properties. While, a ferromagnetic (FM) behavior with a Curie temperature of 1.85 K has been found in the EBTO3-delta thin films. Spin-polarized Ti3+ ions, which originated from the V-O, has been proven to mediate a FM coupling between the local Eu 4f spins and were believed to be responsible for the great change of the magnetic ordering. Considering the easy formation of V-O, our work opens up a new avenue for achieving co-existence of FM and FE orders in oxide materials.