  Super-exchange most often leads to antiferromagnetim in transition-metal
perovskite oxides, yet ferromagnetism or ferrimagnetism would be preferred for
many applications, for example in data storage. While alloying, epitaxial
strain and defects were shown to lead to ferromagnetism, engineering this
magnetic order remains a challenge. We propose, based on density functional
theory calculations, a novel route to defect-engineer ferrimagnetism, which is
based on preferential displacements of oxygen vacancies due to finite
temperature vibrations. This mechanism has an unusual temperature dependence,
as it is absent at 0K, strengthens with increasing temperature before vanishing
once oxygen vacancies disorder, giving it a unique experimentally detectable
signature.
