  Interface physics in oxide heterostructures is pivotal in material's science.
Domain walls (DWs) in ferroic systems are examples of naturally occurring
interfaces, where order parameter of neighboring domains is modified and
emerging properties may develop. Here we show that electric tuning of
ferroelastic domain walls in SrTiO3 leads to dramatic changes of the magnetic
domain structure of a neighboring magnetic layer (La1/2Sr1/2MnO3) epitaxially
clamped on a SrTiO3 substrate. We show that by exploiting the resposiveness of
DWs nanoregions to external stimuli, even in absence of any domain
contribution, prominent and adjustable macroscopic reactions of neighboring
layers can be obtained. We conclude that polar DWs, known to exist in other
materials, can be used to trigger tunable responses and may lead to new ways
for manipulation of interfacial emerging properties.
