H. Bouyanfif

Université de Fribourg, Fribourg, FR, Switzerland

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Publications (4)75.27 Total impact

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    ABSTRACT: Artificial multilayers offer unique opportunities for combining materials with antagonistic orders such as superconductivity and ferromagnetism and thus to realize novel quantum states. In particular, oxide multilayers enable the utilization of the high superconducting transition temperature of the cuprates and the versatile magnetic properties of the colossal-magnetoresistance manganites. However, apart from exploratory work, the in-depth investigation of their unusual properties has only just begun. Here we present neutron reflectometry measurements of a [Y(0.6)Pr(0.4)Ba(2)Cu(3)O(7) (10 nm)/La(2/3)Ca(1/3)MnO(3) (10 nm)](10) superlattice, which reveal a surprisingly large superconductivity-induced modulation of the vertical ferromagnetic magnetization profile. Most surprisingly, this modulation seems to involve the density rather than the orientation of the magnetization and is highly susceptible to the strain, which is transmitted from the SrTiO(3) substrate. We outline a possible explanation of this unusual superconductivity-induced phenomenon in terms of a phase separation between ferromagnetic and non-ferromagnetic nanodomains in the La(2/3)Ca(1/3)MnO(3) layers.
    Nature Material 03/2009; 8(4):315-9. · 35.75 Impact Factor
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    ABSTRACT: Electronic devices that use the spin degree of freedom hold unique prospects for future technology. The performance of these 'spintronic' devices relies heavily on the efficient transfer of spin polarization across different layers and interfaces. This complex transfer process depends on individual material properties and also, most importantly, on the structural and electronic properties of the interfaces between the different materials and defects that are common to real devices. Knowledge of these factors is especially important for the relatively new field of organic spintronics, where there is a severe lack of suitable experimental techniques that can yield depth-resolved information about the spin polarization of charge carriers within buried layers of real devices. Here, we present a new depth-resolved technique for measuring the spin polarization of current-injected electrons in an organic spin valve and find the temperature dependence of the measured spin diffusion length is correlated with the device magnetoresistance.
    Nature Material 12/2008; 8(2):109-14. · 35.75 Impact Factor
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    ABSTRACT: We investigated with synchrotron x-ray diffraction and reflectometry the formation of structural domains in the near-surface region of single crystalline SrTiO3 (001) substrates with Y0.6Pr0.4Ba2Cu3O7/La2/3Ca1/3MnO3 superlattices grown on top. We find that the antiferrodistortive cubic to tetragonal transition, which occurs at TSTO=104K in the bulk and at a considerably higher temperature of at least 120 K in the surface region of SrTiO3 , has only a weak influence on the domain formation. The strongest changes occur instead in the vicinity of the tetragonal to orthorhombic transition in SrTiO3 around 65 K where pronounced surface facets develop that reach deep (at least several micrometers) into the SrTiO3 substrate. These micrometer-sized facets are anisotropic and tilted with respect to one another by up to 0.5° along the shorter direction. Finally, we find that a third structural transition below 30 K gives rise to significant changes in the spread of the c -axis parameters. Overall, our data provide evidence for a strong mutual interaction between the structural properties of the SrTiO3 surface and the multilayer grown on top.
    Physical review. B, Condensed matter 01/2008; 78(13). · 3.77 Impact Factor
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    ABSTRACT: We investigated with synchrotron x-ray diffraction and reflectometry the formation of structural domains in the near-surface region of single crystalline SrTiO3 (001) substrates with Y0.6Pr0.4Ba2Cu3O7/La2/3Ca1/3MnO3 superlattices grown on top. We find that the antiferrodistortive cubic to tetragonal transition, which occurs at TSTO=104 K in the bulk and at a considerably higher temperature of at least 120 K in the surface region of SrTiO3, has only a weak influence on the domain formation. The strongest changes occur instead in the vicinity of the tetragonal to orthorhombic transition in SrTiO3 around 65 K where pronounced surface facets develop that reach deep (at least several micrometers) into the SrTiO3 substrate. These micrometer-sized facets are anisotropic and tilted with respect to one another by up to 0.5° along the shorter direction. Finally, we find that a third structural transition below 30 K gives rise to significant changes in the spread of the c-axis parameters. Overall, our data provide evidence for a strong mutual interaction between the structural properties of the SrTiO3 surface and the multilayer grown on top.
    Phys. Rev. B. 78(13).