Showing papers by "Michel Viret published in 2009"

Electric Field Switching of the Magnetic Anisotropy of a Ferromagnetic Layer Exchange Coupled to the Multiferroic Compound BiFeO 3

Abstract: We report here that a Permalloy layer deposited on top of a multiferroic ${\mathrm{BiFeO}}_{3}$ single crystal acquires an easy magnetic direction along the propagation vector of the cycloidal arrangement of antiferromagnetic moments in ${\mathrm{BiFeO}}_{3}$. This anisotropy originates from a direct magnetic coupling with the canted spins forming the cycloid. Moreover, we show that an electric field-induced change of electric polarization is able to toggle the direction of anisotropy in the ferromagnet through the magnetoelectric effect, which links the antiferromagnetic spins to the local polarization in ${\mathrm{BiFeO}}_{3}$.

Artificial antiphase boundary at the interface of ferrimagnetic spinel bilayers

Abstract: ${\text{CoFe}}_{2}{\text{O}}_{4}/{\text{Fe}}_{3}{\text{O}}_{4}$ bilayers represent an unusual exchange-coupled system whose properties are due to the nature of the oxide-oxide superexchange interactions at the interface. In this work, we analyze the magnetization reversal behavior and magnetic interface structure using a variety of advanced techniques. Low-temperature magnetization, magnetotransport, and polarized neutron reflectivity measurements suggest that the magnetization configuration at the bilayer interface mimics that of an antiphase boundary found in spinel ferrite thin films, thus explaining the unique nature of the magnetic behavior.

Microstructural and magnetic study of Fe-implanted 6H-SiC

Abstract: Single crystalline 6H-SiC near (0 0 0 1)-oriented p-type samples were co-implanted at 550 °C with Fe ions at different energies and fluences ranging from 30 to 160 keV and from 2×10 15 to 8×10 15 ions cm −2 with the aim to get so-called diluted magnetic semiconductors (DMS). Different treatments for implantation-induced damage recovery and iron incorporation and activation in the SiC matrix have been studied: the effects of rapid thermal annealing (RTA) on microstructure and magnetic properties of Fe-implanted 6H-SiC are compared to those of laser processing in the solid phase.

Normal and reversed tunable magnetoresistance in a NiOx/p-doped silicon diode

Abstract: Nonstoichiometric NiOx thin films fabricated by heating in air nickel thin films sputtered on p-doped silicon substrates show a superparamagnetic magnetization and frustrated magnetism with transition temperatures of 200–300 K. Transport measurements across the magnetic/semiconductor bilayer have a rectifying I-V and voltage dependent magnetoresistance, with maximum ratios at 77 K and 2 T of 70% and −17%. The effect is explained in terms of field dependent polarization in granular NiOx and highly efficient spin filtering/injection.