  Oxygen vacancies (VOs) 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 VOs. 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 VOs, 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. Our work opens up a new avenue for developing FM-FE materials by
manipulating the oxygen deficiency in AFM-FE multiferroics.
