Browsing by Author "Barthélémy, A"

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    Crafting 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, M
    Multiferroics 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.
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    Electric control of spin wave modes at room temperature in BiFeO3
    (Australian Institute of Physics, 2012-02-01) Rovillain, P; de Sousa, R; Gallais, Y; Sacuto, A; Measson, MA; Colson, D; Forget, A; Bibes, M; Barthélémy, A; Cazayous, M
    Multiferroic materials present the rare case to exhibit simultaneously magnetic and ferroelectric orders in interaction. This interaction corresponds to the magnetoelectric coupling. Thereby, magnetoelectric materials can potentially be used to control spins by an external electric field. This feature seems promising in spintronics and in magnonics that use magnetic excitations (spin wave) for information processing. In BiFeO3, a room-temperature magnetoelectric material, the interaction between the ferroelectric and magnetic orders offers the opportunity to control spins with an electric field. We have detected by Raman scattering two species of spin propagation modes (magnon) in BiFeO3 single crystal: in-plane (phi mode) and modes out of the cycloidal plane (psi mode) [1,2]. The frequencies of these modes have been successfully compared to the results of a Ginzburg-Landau mode [3]. Our result shows that the magnon modes might be interpreted as electromagnon. In order to characterize the magnetoelectric coupling, an external electric field has been applied. We show that in BiFeO3, the spin-wave frequency can be tuned electrically by over 30%, in a non-volatile way and with virtually no power dissipation [4]. These results showed that BiFeO3 is a very promising material for the generation and the control of spin waves in the future magnonic devices.