Alexandre Pasko

XXIst Century Ferrites

Ferrites have always been a subject of great interest from point of view of magnetic application, since the fist compass to present date. In contrast, the scientific interest for iron based magnetic oxides decreased after Orsted discovery as they where replaced by coil as magnetizing sources. Neel discovery of ferrimagnetism boosted again interest and leads to strong developments during two decades before being of less interest. Recently, the evolution of power electronics toward higher frequency, the downsizing of ceramics microstucture to nanometer scale, the increasing price of rare-earth elements and the development of magnetocaloric materials put light again on ferrites. A review on three ferrite families is given herein: harder nanostructured Ba2+Fe12O19 magnet processed by spark plasma sintering, magnetocaloric effect associated to the spin transition reorientation of W-ferrite and low temperature spark plasma sintered Ni-Zn-Cu ferrites for high frequency power applications.

Growth and characterization of ferrite film prepared by pulsed laser deposition

Ba2+Fe12O19 (BaO.6Fe2O3) films have been grown on (0001) sapphire substrate using pulsed laser deposition (PLD) technique. Prepared films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray reflectivity (XRR), atomic force microscopy (AFM) and magnetic measurements. XRD confirms the formation of Ba2+Fe12O19 phase, whereas presence of Fe2O3 was also identified. X-ray photoelectron spectroscopy (XPS) shows the signature of all the elements present in the barium ferrite. XRR data show the thickness of the film is ~ 24.2 nm with top layer roughness of ~ 3.7 nm. AFM measurement suggests the formation of clusters with average roughness of ~ 3.9 nm. Magnetic measurements of the target reveal its anisotropic nature with coercivity values: 0.23 and 0.24 T, obtained along two orthogonal directions. For the prepared thin film, the obtained coercivity ~80 mT and saturation induction 0.13 T are lower than the usual values obtained for Ba2+Fe12O19 compound (coercivity and saturation induction values are 0.19 Tesla and 0.48 T respectively), can be ascribed to the presence of Fe2O3 phase.