Magnetic Nernst effect

The thermodynamics of irreversible processes in continuous media predicts the existence of a Magnetic Nernst effect that results from a magnetic analog to the Seebeck effect in a ferromagnet and magnetophoresis occurring in a paramagnetic electrode in contact with the ferromagnet. Thus, a voltage that has DC and AC components is expected across a Pt electrode as a response to the inhomogeneous magnetic induction field generated by magnetostatic waves of an adjacent YIG slab subject to a temperature gradient. The voltage frequency and dependence on the orientation of the applied magnetic induction field are quite distinct from that of spin pumping.Comment: 4 pages, 1 figur

Evidence for thermal spin transfer torque

Large heat currents are obtained in Co/Cu/Co spin valves positioned at the middle of Cu nanowires. The second harmonic voltage response to an applied current is used to investigate the effect of the heat current on the switching of the spin valves. Both the switching field and the magnitude of the voltage response are found to be dependent on the heat current. These effects are evidence for a thermal spin transfer torque acting on the magnetization and are accounted for by a thermodynamic model in which heat, charge and spin currents are linked by Onsager reciprocity relations.Comment: 4 pages, 4 figure

Thermodynamics of a continuous medium with electric and magnetic dipoles

The thermodynamics of an electrically charged, multicomponent fluid with spontaneous electric and magnetic dipoles is analysed in the presence of electromagnetic fields. Taking into account the chemical composition of the current densities and stress tensors leads to three types of irreversible terms: scalars, vectors and pseudo-vectors. The scalar terms account for chemical reactivities, the vectorial terms account for transport and the pseudo-vectorial terms account for relaxation. The linear phenomenological relations, derived from the irreversible evolution, describe notably the Lehmann and electric Lehmann effects, the Debye relaxation of polar molecules and the Landau-Lifshitz relaxation of the magnetisation. This formalism accounts for the thermal and electric magnetisation accumulations and magnetisation waves. It also predicts that a temperature gradient affects the dynamics of magnetic vortices and drives magnetisation wave

Rotational Heisenberg Inequalities

Since their discovery in 1927, the Heisenberg Inequalities have become an icon of quantum mechanics. Often inappropriately referred to as the Uncertainty Principle, these inequalities relating the standard deviations of the position and momentum observables to Planck's constant are one of the cornerstones of the quantum formalism even if the physical interpretation of quantum mechanics remains still open to controversy nowadays. The Heisenberg Inequalities governing translational motion are well understood. However, the corresponding inequalities pertaining to rotational motion have not been established so far. To fill this gap, we present here the Rotational Heisenberg Inequalities relating the standard deviations of the orientation axis and orbital angular momentum observables of an isolated molecule. The reason for choosing this system is that a molecule separated from its environment corresponds to a bound system preserving the orbital angular momentum.Comment: 6 pages, 2 figures. arXiv admin note: substantial text overlap with arXiv:1412.211

Thermodynamics of a continuous medium with electric dipoles and magnetic moments

The thermodynamics of an electrically charged, multicomponent fluid with spontaneous electric dipoles and magnetic moments is analysed in the presence of electromagnetic fields. Taking into account the chemical composition of the current densities and stress tensors leads to three types of dissipation terms: scalars, vectors and pseudo-vectors. The scalar terms account for chemical reactivities, the vectorial terms account for transport and the pseudo-vectorial terms account for relaxation. The linear phenomenological relations, derived from the irreversible evolution, describe notably the Lehmann and electric Lehmann effects, the Debye relaxation of polar molecules and the Landau-Lifshitz relaxation of the magnetisation. This formalism accounts for the thermal and electric magnetisation accumulations and magnetisation waves. It also predicts that a temperature gradient affects the dynamics of magnetic vortices and drives magnetisation waves

L'enseignement au régime planétaire

La création d'un MOOC (massive open on-line course) nécessite une infrastructure technique poussée et la collaboration de plusieurs acteurs. Ces conditions cadres sont analysées sur la base de l'expérience acquise lors de la création d'un MOOC de mécanique, fournissant des données numériques pour la planification d'une telle entreprise. Le rayonnement international et l'impact local d'un MOOC présentent de nouveaux défis et suscitent de nouvelles initiatives pédagogiques

Pulsed magnetic resonance of Alq3 OLED detected by electroluminescence

The aim of the present work is to investigate the nature of spin dependent processes in an organic light emitting diode based on a ITO/α-NPD/Alq3 structure. The electroluminescence time response of the sample is monitored while the OLED is exposed to a high power resonant microwave pulse. Measurements are carried out at room temperature. The time scale of the induced transition is found to be independent of the bias voltage. It is shown, by way of a simulation, that this behavior appears inconsistent with models which attribute a change in the electroluminescence to a variation in charge mobility. Spin dependent processes directly related to a change in the rate of charge recombination play therefore a relevant role in Alq3 light emitting diodes

Evidence for a Magnetic Seebeck effect

The irreversible thermodynamics of a continuous medium with magnetic dipoles predicts that a temperature gradient in the presence of magnetisation waves induces a magnetic induction field, which is the magnetic analog of the Seebeck effect. This thermal gradient modulates the precession and relaxation. The Magnetic Seebeck effect implies that magnetisation waves propagating in the direction of the temperature gradient and the external magnetic induction field are less attenuated, while magnetisation waves propagating in the opposite direction are more attenuated

CdTe semiconductor nanowires and NiFe ferro-magnetic metal nanowires electrodeposited into cylindrical nano-pores on the surface of anodized aluminum

Cylindrical nano-pores of an anodized aluminum oxide layer on the surface of bulk aluminum were used as templates for the electrochemical growth of semiconductor and magnetic nanowires. The electrodeposition of CdTe and NiFe was investigated to determine the optimum conditions for each nanowire growth over a wide range of cathode potentials. The desired composition of Cd50Te50 and Ni80Fe20 was achieved by controlling the cathode potential during electrodeposition. Temperature dependences of resistance for CdTe nanowires confirmed the semiconductor character with amorphous behavior at low temperature, while those of NiFe nanowires showed metallic character. The anisotropic magnetoresistance (AMR) of NiFe nanowires reached 1.9% at 300

Thermodynamics of continuous media with intrinsic rotation and magnetoelectric coupling

The thermodynamics of an electrically charged, multicomponent continuous medium with intrinsic rotation is analysed in the presence of electromagnetic fields with a weak linear magnetoelectric coupling in the non-relativistic limit. Taking into account the chemical composition of the current densities and stress tensors yields scalar dissipation terms accounting for chemical reactivities and vectorial dissipation terms accounting for transport. Three equations characterising the continuous medium are derived: a thermostatic equilibrium equation, a reversible and an irreversible thermodynamic evolution equation. Explicit expressions for the temperature and the chemical potentials are derived in terms of the electromagnetic fields and the magnetoelectric coupling. The transport equations contain electromagnetic terms normally not included in a standard thermodynamic phenomenology