Browsing by Author "Toulouse, C"
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- ItemCrafting the magnonic and spintronic response of BiFeO3 films by epitaxial strain(Nature Publishing Group, 2013-04-28) Sando, D; Agbelele, A; Rahmedov, D; Liu, J; Rovillain, P; Toulouse, C; Infante, IC; Pyatakov, AP; Fusil, S; Jacquet, E; Carrétéro, C; Deranlot, C; Lisenkov, S; Wang, D; Le Breton, JM; Cazayous, M; Sacuto, A; Juraszek, J; Zvezdin, AK; Bellaiche, L; Dkhil, B; Barthélémy, A; Bibes, MMultiferroics are compounds that show ferroelectricity and magnetism. BiFeO3, by far the most studied, has outstanding ferroelectric properties, a cycloidal magnetic order in the bulk, and many unexpected virtues such as conductive domain walls or a low bandgap of interest for photovoltaics. Although this flurry of properties makes BiFeO3 a paradigmatic multifunctional material, most are related to its ferroelectric character, and its other ferroic property—antiferromagnetism—has not been investigated extensively, especially in thin films. Here we bring insight into the rich spin physics of BiFeO3 in a detailed study of the static and dynamic magnetic response of strain-engineered films. Using Mössbauer and Raman spectroscopies combined with Landau–Ginzburg theory and effective Hamiltonian calculations, we show that the bulk-like cycloidal spin modulation that exists at low compressive strain is driven towards pseudo-collinear antiferromagnetism at high strain, both tensile and compressive. For moderate tensile strain we also predict and observe indications of a new cycloid. Accordingly, we find that the magnonic response is entirely modified, with low-energy magnon modes being suppressed as strain increases. Finally, we reveal that strain progressively drives the average spin angle from in-plane to out-of-plane, a property we use to tune the exchange bias and giant-magnetoresistive response of spin valves. © 2013, Nature Publishing Group.
- ItemLattice and spin excitations in multiferroic h-YbMnO3(American Physical Society, 2012-11-09) Liu, J; Toulouse, C; Rovillain, P; Cazayous, M; Gallais, Y; Measson, MA; Lee, N; Cheong, SW; Sacuto, ALattice and spin excitations have been studied by Raman scattering in hexagonal YbMnO3 single crystals. The temperature dependences of the phonon modes show that the E-2 mode at 256 cm(-1) related to the displacement of Mn and O ions in a-b plane is coupled to the spin order. The A(1) phonon mode at 678 cm(-1) presents a soft mode behavior at the Neel temperature. Connected to the motion of the apical oxygen ions along the c direction, this mode controls directly the Mn-Mn interactions between adjacent Mn planes and the superexchange path. Crystal field and magnon mode excitations have been identified. The temperature investigation of the spin excitations shows that the spin structure is strongly influenced by the Yb-Mn interaction. Under a magnetic field along the c axis, we have investigated the magnetic reordering and its impact on the spin excitations. © 2012, American Physical Society.