R. Guillemet

Université Paris-Sud 11, Paris, Ile-de-France, France

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Publications (5)48.93 Total impact

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    ABSTRACT: We report on a bottom-up approach for the fabrication of spin-transfer nano-oscillators (STNOs). Porous alumina is used as a template for the growth by electrodeposition of metallic spin valves in series. Under specific magnetic field and injected current conditions, emission of microwave current is detected with frequency in the 1.5 GHz range and linewidth as low as 8 MHz. We find strong indications that the microwave emission is due to spin-transfer-driven vortex oscillations. This technique is promising for the fabrication of dense arrays of STNOs in view of device synchronization.
    Journal of Physics D Applied Physics 02/2011; 44(10):105003. · 2.53 Impact Factor
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    ABSTRACT: Molecular and organic spintronics offers the opportunity to play with chemical versatility and to bring the spin degree of freedom to electronics devices. We will show how, as a contender to commonly used inorganic materials, organic/molecular based spintronics devices can exhibit very large magnetoresistance and lead to tailored spin polarizations. First we will report on giant tunnel magnetoresistance of up to 300% in a (La,Sr)MnO3/Alq3/Co nanometer size magnetic tunnel junctions. Samples are nanofabricated using a conductive tip AFM nanolithography process in order to circumvent problems such as inhomogeneity and strong metal diffusion. In a second part we will present a spin dependent transport model giving a new understanding of spin injection into organic materials. We will show how one could tune spin injection by molecular engineering.
    03/2010;
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    ABSTRACT: Synchronized spin-valve oscillators may lead to nanosized microwave generators that do not require discrete elements such as capacitors or inductors. Uniformly magnetized oscillators have been synchronized, but offer low power. Gyrating magnetic vortices offer greater power, but vortex synchronization has yet to be demonstrated. Here we find that vortices can interact with each other through the mediation of antivortices, leading to synchronization when they are closely spaced. The synchronization does not require a magnetic field, making the system attractive for electronic device integration. Also, because each vortex is a topological soliton, this work presents a model experimental system for the study of interacting solitons.
    Nature Nanotechnology 09/2009; 4(8):528-32. · 31.17 Impact Factor
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    ABSTRACT: Spin-transfer torque effects are reported in nanowires consisting in Co/Cu/Co trilayers electrodeposited on an anodic alumina template. Using a nanolithography process based on electrically controlled nanoindentation of the alumina template, we are able to investigate the spin transport properties of single nanowires at room temperature. For small applied magnetic fields, we have measured resistance changes above a critical direct-current (dc) injected current that corresponds to the change in resistance observed in the magnetoresistance curves at low current. We conclude that magnetic reversals are driven by a spin-polarized current. The critical current densities needed for the magnetization reversals are in the 107 A/cm2 range and the dependence of the critical currents with the applied field is consistent with the spin-transfer mechanism. For large applied magnetic fields, the differential resistance exhibits some peaks that we attribute to the onset of high-frequency excitations of the free-layer magnetization. According to the high density of electrodeposited nanowires in alumina templates, our results are promising for synchronized spin-transfer oscillators.
    Journal of Applied Physics 11/2007; 102(10):103906-103906-5. · 2.21 Impact Factor
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    ABSTRACT: We have developed a new reliable method combining template synthesis and nanolithography-based contacting technique to elaborate current perpendicular-to-plane giant magnetoresistance spin valve nanowires, which are very promising for the exploration of electrical spin transfer phenomena. The method allows the electrical connection of one single nanowire in a large assembly of wires embedded in anodic porous alumina supported on Si substrate with diameters and periodicities to be controllable to a large extent. Both magnetic excitations and switching phenomena driven by a spin-polarized current were clearly demonstrated in our electrodeposited NiFe/Cu/ NiFe trilayer nanowires. This novel approach promises to be of strong interest for subsequent fabrication of phase-locked arrays of spin transfer nano-oscillators with increased output power for microwave applications.
    Nano Letters 10/2007; 7(9):2563-7. · 13.03 Impact Factor