We have constructed a new concept device with combination of ferroelectric and ferromagnetic materials by a laser ablation technique. An ideal hetero-epitaxy can be obtained owing to the similar crystal structure of perovskite type ferroelectric Pb (Zr, Ti) O3; (so called PZT) and ferromagnetic (La, Sr) MnO3. The ferromagnetic (La, Sr) MnO3 compounds are well known for their colossal magnetoresistance (CMR) properties. The CMR effect is strongly affected by the lattice stress. The PZT, on the other hand, is famous for its large piezoelectrics. We can introduce the lattice stress easily by applying voltage for the piezoelectric compounds. In the heterostructured ferromagnetic/ferroelectric devices, there are remarkable interesting phenomena. Electric properties of the ferromagnetic material can be controlled by piezoelectric effect via distortion of crystal structure.

We have constructed Bi based layer structured ferroelectric films and their superlattices by a pulsed laser deposition technique. The dielectric constants along c-axis increase with increasing of the number of pseudo-perovskite layers between double Bi2O2 layers. Ferroelectricity appears along the c-axis direction only for the odd number of the perovskite layers owing to the mirror symmetry in a crystal structure. Especially, the Bi2VO5. 5 film shows an atomically flat surface, low dielectric constant of 30 and ferroelectricity of Pr=3 µC/cm2 and Ec=16 kV/cm, respectively. This material is expected to the application for FRAMs.

Ferroelectric / superconducting heterostructures of Pb(Zr0.52Ti0.48)O3 [PZT] / (Y0.6Pr0.4)Ba2Cu3Oy [YPBCO] have been formed on SrTiO3(100) substrate using an ArF pulsed laser deposition. The crystallinity and surface morphology of heterostructures were investigated by X-ray diffraction measurements and atomic force microscopy. We also measured dielectric and ferroelectric properties of PZT film in the Au/PZT/YPBCO structure. Furthermore, we fabricated a three-terminal devices having the structure described above using an in-situ metal mask exchange system, and investigated the ferroelectric field effect. As a result, we observed a modulation of channel resistance approximately equal to that estimated from the induced carrier and memory effect due to remanent polarization of PZT.