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M Viret

Publications and source records attributed to M Viret.

8 recordsLinked to original sources
PubMed2004

Magnetic filaments in resistive manganites.

The magnetic phase separation in single crystals of the Pr0.67Ca0.33MnO3 manganites is studied using polarized small angle neutron scattering. The measured spectra give a fractal dimension consistent with a configuration in ferromagnetic filaments of nanometric diameter. We argue here that localized charge carriers hop in a random walk fashion mediating a ferromagnetic "hopping exchange" which coexists with superexchange to create the filamentary phase separation. The arguments for this physical picture are validated by Monte Carlo simulations, where magnetism and transport are treated in a self-consistent manner.

Journal Article↗
PubMed2002

Individual domain wall resistance in submicron ferromagnetic structures.

The resistance generated by individual domain walls is measured in a FePd nanostructure. Combining transport and magnetic imaging measurements, the intrinsic domain wall resistance is quantified. It is found positive and of a magnitude consistent with that predicted by models based on spin scattering effects within the walls. This magnetoresistance at a nanometer scale allows a direct counting of the number of walls inside the nanostructure. The effect is then used to measure changes in the magnetic configuration of submicron stripes under application of a magnetic field.

Journal Article↗
PubMed2000

Anisotropy of domain wall resistance

The resistive effect of domain walls in FePd films with perpendicular anisotropy was studied experimentally as a function of field and temperature. The films were grown directly on MgO substrates, which induces an unusual virgin magnetic configuration composed of 60 nm wide parallel stripe domains. This allowed us to carry out the first measurements of the anisotropy of domain wall resistivity in the two configurations of current perpendicular and parallel to the walls. At 18 K, we find 8.2% and 1.3% for the domain wall magnetoresistance normalized to the wall width (8 nm) in these two respective configurations. These values are consistent with the predictions of Levy and Zhang.

Journal Article↗