CoFe 2 O 4 (CFO)/BaTiO 3 (BTO)/CoFe 2 O 4 (CFO) multilayered thin films were deposited on Pt/TiO 2 /SiO 2 /Si substrates by the pulsed laser deposition (PLD) system with KrF excimer laser (λ = 248 nm). BTO, CFO, BTO/ CFO and CFO/BTO/CFO structured thin films were prepared and their crystal structures and microstructures, as well as their magnetic and magneto-electrical properties, were studied. The C-V characteristics of these multilayered thin films with different capacitor structures were obtained to confirm the change in their capacitances under a magnetic field. Finally, the capacitance of the CFO/BTO/CFO thin film as a function of bias voltage under an in-plane magnetic field of 1,000 Oe increased to 951.04 pF at 1 MHz, from 831.90 pF measured under no magnetic field, indicating 14.3% increase in magnetocapacitance.

The magnetostriction effect, the change in the mechanical properties of a magnetic material in an external magnetic field, has been studied for possible technological applications such as actuators. We present the fabrication of a multilayered magnetocapacitor containing magnetic layers of Ni0.98Co0.02Fe2O4 (NCFO) and compare it with our prior magnetocapacitor in which CoFe2O4 (CFO) and CoNiFe (CNF) were used as the magnetic layers. In particular, we measured the surface/interface microstructures and the change in the lattice constant of the BaTiO3 (BTO) film in NCFO/BTO/NCFO, CFO/BTO/CFO, and CNF/BTO/CNF multilayered thin films. Our study suggests that there is a correlation exists between the magnetocapacitance and the lattice constant of BTO, which varies with the type of ferromagnetic (FM) material embedded in the magnetic layer.

We report the fabrication of a multilayer magnetocapacitor from the highly magnetostrictive material Ni 0.98 Co 0.02 Fe 2 O 4 . To fabricate the magnetocapacitor, Ni 0.98 Co 0.02 Fe 2 O 4 /BaTiO 3 /Ni 0.98 Co 0.02 Fe 2 O 4 sandwich-type multilayer thin films were deposited on Pt/TiO 2 /SiO 2 /Si(100) substrates by pulsed laser deposition. We studied the crystal structures, the surface and interface microstructures, and the magnetic and electric properties of multilayer thin films with different thickness of Ni 0.98 Co 0.02 Fe 2 O 4 (20, 60, and 150 nm) and BaTiO 3 (100, 300, and 1000 nm).

The Fe 3 O 4 nanoparticle was synthesized by the hot-injection method while varying the injection time of the precursor solution. The crystal structure was determined to be cubic inverse spinel with space group of Fd-3m based on X-ray diffraction (XRD) measurements and the morphology of the prepared Fe 3 O 4 nanoparticle was studied with a high-resolution transmission electron microscope (HR-TEM). When the precursor solution was injected for 0.5 min, the size of the Fe 3 O 4 nanoparticle was 7.63 nm, while the size of the obtained particle was 21.27 nm with the injection time of 60 min. The magnetic properties of the prepared Fe 3 O 4 nanoparticle were investigated by both vibrating sample magnetometer (VSM) and 57Co Mössbauer spectroscopy at various temperatures. From the hyperthermia measurement, we observed that the temperature of the Fe 3 O 4 nanoparticle powder reached around 120 o C under 250 Oe at 50 kHz, when the injection time of the precursor solution was 60 min.