  We report on linear and non-linear dielectric property measurements of BaTiO3
- CoFe2O4 (BTO-CFO) ferroelectro-magnetic nano-composites and pure BaTiO3 and
CoFe2O4 samples with Scanning Near Field Microwave Microscopy. The permittivity
scanning image with spatial resolution on the micro-meter scale shows that the
nano-composites have very uniform quality with an effective dielectric constant
\epsilon_r = 140 +/- 6.4 at 3.8 GHz and room temperature. The temperature
dependence of dielectric permittivity shows that the Curie temperature of pure
BTO was shifted by the clamping effect of the MgO substrate, whereas the Curie
temperature shift of the BTO ferroelectric phase in BTO-CFO composites is less
pronounced, and if it exists at all, would be mainly caused by the CFO.
Non-linear dielectric measurements of BTO-CFO show good ferroelectric
properties from BTO.
