Switching the magnetic configuration of a spin valve by current induced domain wall motion

We present experimental results on the displacement of a domain wall by injection of a dc current through the wall. The samples are 1 micron wide long stripes of a CoO/Co/Cu/NiFe classical spin valve structure. The stripes have been patterned by electron beam lithography. A neck has been defined at 1/3 of the total length of the stripe and is a pinning center for the domain walls, as shown by the steps of the giant magnetoresistance curves at intermediate levels (1/3 or 2/3) between the resistances corresponding to the parallel and antiparallel configurations. We show by electric transport measurements that, once a wall is trapped, it can be moved by injecting a dc current higher than a threshold current of the order of magnitude of 10^7 A/cm^2. We discuss the different possible origins of this effect, i.e. local magnetic field created by the current and/or spin transfer from spin polarized current.Comment: 3 pages, 3 figure

Spin injection in a single metallic nanoparticle: a step towards nanospintronics

We have fabricated nanometer sized magnetic tunnel junctions using a new nanoindentation technique in order to study the transport properties of a single metallic nanoparticle. Coulomb blockade effects show clear evidence for single electron tunneling through a single 2.5 nm Au cluster. The observed magnetoresistance is the signature of spin conservation during the transport process through a non magnetic cluster.Comment: 3 page

Study of the magnetic order in a Co/Cr multilayer by magnetic bragg diffraction at the Co 2p resonance

We have measured the resonant scattering from an antiferromagnetic Co/Cr multilayer at photon energies close to the cobalt 2p --> 3d transitions. The cobalt dielectric tensor has an anisotropic component, enhanced by resonance, which depends on the magnetic order and follows its modulation inside the sample. We have studied the vertical distribution of this component through the dependence of the reflectivity on the scattering angle. Using s-polarized light, we have observed the signature of the cobalt-cobalt antiferromagnetic coupling as an half-integer-order Bragg peak. Experimental results have been analyzed by numerical simulation. (C) 2000 Elsevier Science B.V. All rights reserved

Effects of a thin Mg layer on the structural and magnetoresistance properties of CoFeB/MgO/CoFeB magnetic tunnel junctions

International audienceWe have combined in situ reflection high energy electron diffraction, high-resolution transmission electron microscopy, and magnetotransport experiments to investigate the role of a thin inserted Mg layer on the crystalline texture of MgO barriers in magnetic tunnel junctions grown in a standard sputtering system. It was found that an ultrathin Mg layer of 2-6 angstrom can efficiently promote a MgO (001) texture prior to any annealing. For thicker Mg layers, the MgO (001) texture was found to degrade due to the hexagonal structure of Mg. For tunneling magnetoresistance (TMR), the efficient role of the MgO crystallization induced by the Mg layer appears after a 400 degrees C annealing. The optimum was found for a 4 angstrom inserted Mg layer with a TMR of 120% at room temperature (210% at 3 K) which could be considerably improved for fully (001) oriented magnetic tunnel junctions. (c) 2007 American Institute of Physics. (c) 2007 American Institute of Physics

Electrodeposition of patterned magnetic nanostructures

We report on fabrication and characterization of two types of devices, both with submicronic dimensions, and fabricated by combining lithography and electrodeposition. The first device, obtained by combining electron-beam lithography and electrodeposition, was devised to measure the current perpendicular to the plane giant magnetoresistance (CPP-GMR) of a single permalloy/ copper multilayered nanopillar (height similar to 0.3 mu m, diameter similar to 0.1 mu m). Besides the fundamental interest of the spin-dependent transport properties in such nanoscaled magnets, this system is a potential candidate as a CPP-GMR sensor used, for example, to read very high-density magnetic storage. The second device, relevant for high-density storage media, consists in large areas (4 x 4 mm(2)) of magnetic permalloy dots (diameter similar to 0.26 mu m, period similar to 0.4 mu m) electrodeposited in a x-ray patterned photoresist matrix. We study the magnetic behavior of such mesoscopic pillars as a function of their height. We emphasize that our processes are less damaging for the nanostructures, in comparison with samples prepared by high vacuum deposition followed by lithography. This is because our magnetic nanostructures are electrodeposited after the whole lithographic process. (C) 1998 American Institute of Physics. [S0021-8979(98)00923-2]

Conducting tip atomic force microscopy analysis of aluminum oxide barrier defects decorated by electrodeposition

We show that the electrodeposition of Ni80Fe20 on top of a thin aluminum oxide barrier leads to particle growth occurring on preferential nucleation centers. The particle sites are attributed to local defects in the aluminum oxide barrier. As a function of the thickness of the barrier, different growth modes can occur. For thinner barriers, new nucleation centers are created during electrodeposition. The resistance of the defects, characterized by conducting atomic force microscopy, ranges from less than 10(4) to greater than 10(12) Omega. Various I(V) characteristics were also obtained, depending on the resistance of the defect. These results suggest that this experimental technique could be a very interesting one with which to fabricate nanoconstrictions dedicated to ballistic magnetoresistance studies. (C) 2001 American Institute of Physics

Using half-metalilc manganite interfaces to reveal insights into spintronics

A half-metal has been defined as a material with propagating electron states at the Fermi energy only for one of the two possible spin projections, and as such has been promoted as an interesting research direction for spin electronics. This review details recent advances on manganite thin film research within the field of spintronics, before presenting the structural, electronic and spinpolarized solid-state tunnelling transport studies that we have performed on heterostructures involving La2/3Sr1/3MnO3 thin films separated by SrTiO3 barriers. These experiments demonstrate that, with a polarization of spin ↑ electrons at the Fermi level that can reach 99%, the La2/3Sr1/3MnO3/SrTiO3 interface for all practical purposes exhibits half-metallic behaviour. We offer insight into the electronic structure of the interface, including the electronic symmetry of any remaining spin ↓ states at the Fermi level. Finally, we present experiments that use the experimental half-metallic property of manganites as tools to reveal novel features of spintronics