Magnetic field dependence of the effective permittivity in BaTiO₃/Ni nanocomposites observed via microwave spectroscopy

We demonstrate large increases of the real and imaginary parts of the microwave effective complex permittivity of a series of (piezoelectric)BaTiO₃/(magnetostrictive) Ni nanocomposites under the action of a magnetic field, by about 10% at 2 kOe and 300% at 5 kOe, respectively. We suggest that the magnetic field dependence of the effective permittivity is consistent with a magnetoelectric effect which can be qualitatively understood within a model in which the piezoelectric phase is mechanically coupled to the magnetostrictive phase.