High quality epitaxial (SrTiO3/NiO)(n)/MgO thin film multiferroic heterostructures have been fabricated using reactive off-axis sputtering. Crystal quality is verified using x-ray diffraction and ion channeling. These heterostructures comprise of dielectric and antiferromagnetic layers that exhibit dielectric resonance and antiferromagnetic resonance, respectively, at terahertz frequencies. In order to achieve epitaxy despite the large lattice mismatch between SrTiO3 and NiO or MgO, high processing temperature is required. The high temperature has led to a small amount of interdiffusion between any SrTiO3/MgO interfaces. Less interdiffusion is evident for the NiO/MgO interface as seen through Rutherford backscattering. NiO and SrTiO3 have been shown to be compatible and nonreacting at temperatures as high as 1500 degrees C through the use of bulk ceramic techniques. (c) 2007 American Vacuum Society.