Seebeck Effect in Magnetic Tunnel Junctions

Creating temperature gradients in magnetic nanostructures has resulted in a new research direction, i.e., the combination of magneto- and thermoelectric effects. Here, we demonstrate the observation of one important effect of this class: the magneto-Seebeck effect. It is observed when a magnetic configuration changes the charge based Seebeck coefficient. In particular, the Seebeck coefficient changes during the transition from a parallel to an antiparallel magnetic configuration in a tunnel junction. In that respect, it is the analog to the tunneling magnetoresistance. The Seebeck coefficients in parallel and antiparallel configuration are in the order of the voltages known from the charge-Seebeck effect. The size and sign of the effect can be controlled by the composition of the electrodes' atomic layers adjacent to the barrier and the temperature. Experimentally, we realized 8.8 % magneto-Seebeck effect, which results from a voltage change of about -8.7 {\mu}V/K from the antiparallel to the parallel direction close to the predicted value of -12.1 {\mu}V/K.Comment: 16 pages, 7 figures, 2 table

Spin-transfer in an open ferromagnetic layer: from negative damping to effective temperature

Spin-transfer is a typical spintronics effect that allows a ferromagnetic layer to be switched by spin-injection. Most of the experimental results about spin transfer are described on the basis of the Landau-Lifshitz-Gilbert equation of the magnetization, in which additional current-dependent damping factors are added, and can be positive or negative. The origin of the damping can be investigated further by performing stochastic experiments, like one shot relaxation experiments under spin-injection in the activation regime of the magnetization. In this regime, the N\'eel-Brown activation law is observed which leads to the introduction of a current-dependent effective temperature. In order to justify the introduction of these counterintuitive parameters (effective temperature and negative damping), a detailed thermokinetic analysis of the different sub-systems involved is performed. We propose a thermokinetic description of the different forms of energy exchanged between the electric and the ferromagnetic sub-systems at a Normal/Ferromagnetic junction. The corresponding Fokker Planck equations, including relaxations, are derived. The damping coefficients are studied in terms of Onsager-Casimir transport coefficients, with the help of the reciprocity relations. The effective temperature is deduced in the activation regime.Comment: 65 pages, 10 figure

Spin Caloritronics

This is a brief overview of the state of the art of spin caloritronics, the science and technology of controlling heat currents by the electron spin degree of freedom (and vice versa).Comment: To be published in "Spin Current", edited by S. Maekawa, E. Saitoh, S. Valenzuela and Y. Kimura, Oxford University Pres

Sur la biologie d\u27un Alcyonide (Sarcophytum mycetoides Gravier) du Golfe de Tadjourah

Volume: 13Start Page: 434End Page: 43

Note sur une Actinie (Thoracactis n. g., topsenti n.sp.) et un Ann\ue9lide Polych\ue8te (Hermadion Faureli n.sp.), commensaux d\u27une \uc9ponge silicieuse (Sarostegia oculata Topsent)

Volume: 344Start Page: 1End Page: 2

Sur un Crustac\ue9 parasite d\u27un Polyno\uefdien de l\u27Antarctique sud-am\ue9ricaine (Selioides tardus nov. sp.),

Volume: 18Start Page: 63End Page: 6

Sur un nouveau Cop\ue9pode (Flabellicola n.g. neapolitana n. sp) parasite d\u27un Ann\ue9lide polych\ue9te [Flabelligera diplochaitos (Otto)]

Volume: 166Start Page: 502End Page: 50

Sur les Ann\ue9lides Polych\ue8tes de la mer Rouge (Cirratuliens, Spiondiens, Ariciens)

Volume: 11Start Page: 42End Page: 5

Sur les Ann\ue9lides Polych\ue8tes de la mer Rouge, (Nephthydiens Glyc\ue9riens)

Volume: 10Start Page: 472End Page: 47