Title: Evolution of magnetic and dielectric properties in Sr-substituted high temperature multiferroic YBaCuFeO5,
Abstract: We report the evolution of structural, magnetic and dielectric properties due
to partial substitution of Ba by Sr in the high temperature multiferroic
YBaCuFeO5. This compound exhibits ferroelectric and antiferromagnetic
transitions around 200 K and these two phenomena are presumed to be coupled
with each other. Our studies on magnetic and dielectric properties of the
YBa1-xSrxCuFeO5 (x = 0.0, 0.25 and 0.5) show that substitution of Sr shifts
magnetic transition towards higher temperature whereas dielectric transition to
lower temperature. These results points to the fact that magnetic and
dielectric transitions get decoupled as a result of chemical pressure in form
of Sr substitution. The nature of magnetodielectric coupling changes across the
series with the presence of higher order coupling terms. Additionally in these
compounds glassy dynamics of electric dipoles is observed at low temperatures.