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Papers by Cristina Ciornei

A thin ScAlN layer was deposited on high resistivity (111) oriented silicon and two port surface ... more A thin ScAlN layer was deposited on high resistivity (111) oriented silicon and two port surface acoustic wave (SAW) devices were manufactured, using advanced nanolithographic techniques, on this material. The Surface Acoustic Wave and Spin Wave (SAW/SW) coupling was performed via a thin ferromagnetic layer (Ni) placed between the interdigitated transducers (IDTs) of the SAW device. Since the phase velocity in this material is lower than in the Si substrate, both Rayleigh (4.67 GHz) and Sezawa (8.05 GHz) propagation modes could be observed. The amplitude of the S21 parameter around the two resonances was measured for values of the magnetic field µ0H from -280 to +280 mT, at different angles (θ) between the SAW propagation direction and the magnetic field direction. A maximum decrease of 2.54 dB occurred in S21 for the Rayleigh mode at µ0H = -90 mT, and of 7.24 dB for the Sezawa mode at µ0H =-203 mT, both at θ = 45°. These values were extracted from time gated processing of the frequ...

European Journal of Physics, 2016

NATO Advanced Research Workshop on Electron Transport in Nanosystems,, 2008

... T. Wade, J. -E. Wegrowe Procede de fabrication de composants electroniques et composants ... ... more ... T. Wade, J. -E. Wegrowe Procede de fabrication de composants electroniques et composants ... S. Peulon, D. Lincot, Mechanistic Study of cathodic electrodeposition of zinc oxide ... Study on the microstruc-ture and growth mechanism of electrochemical deposited ZnO nanowires. ...

Materials Research Society Symposium Proceedings, 2008

Physical Review B, 2011

The dynamical equation of the magnetization has been reconsidered with enlarging the phase space ... more The dynamical equation of the magnetization has been reconsidered with enlarging the phase space of the ferromagnetic degrees of freedom to the angular momentum. The generalized Landau-Lifshitz-Gilbert equation that includes inertial terms, and the corresponding Fokker-Planck equation, are then derived in the framework of mesoscopic non-equilibrium thermodynamics theory. A typical relaxation time τ is introduced describing the relaxation of the magnetization acceleration from the inertial regime towards the precession regime defined by a constant Larmor frequency. For time scales larger than τ , the usual Gilbert equation is recovered. For time scales below τ , nutation and related inertial effects are predicted. The inertial regime offers new opportunities for the implementation of ultrafast magnetization switching in magnetic devices.

Applied Physics Letters, 2007

Electronic transport properties of silicon nanowires grown by chemical vapor deposition, embedded... more Electronic transport properties of silicon nanowires grown by chemical vapor deposition, embedded in an insulating alumina nanoporous membrane are studied. Transport measurements were performed from 300to4.2K, which revealed a scaling law of the conductance as a function of the temperature and the dc bias voltage, which the authors interpreted as a Coulomb blockade manifestation. Magnetoconductive measurements at low temperature revealed a positive magnetoconductance which can be well fitted by quasi-one-dimensional (quasi-1D) weak localization theory. These results seem to indicate that electron-electron interactions and quasi-1D effect predominate on the electronic transport properties of these systems.

American Journal of Physics, 2012

The gyromagnetic relation—that is, the proportionality between the angular momentum L→ and the ma... more The gyromagnetic relation—that is, the proportionality between the angular momentum L→ and the magnetization M→—is evidence of the intimate connections between the magnetic properties and the inertial properties of ferromagnetic bodies. However, inertia is absent from the dynamics of a magnetic dipole: The Landau–Lifshitz equation, the Gilbert equation, and the Bloch equation contain only the first derivative of the magnetization with respect to time. In order to investigate this paradoxical situation, the Lagrangian approach, proposed originally by Gilbert, is revisited keeping an arbitrary nonzero inertia tensor. The corresponding physical picture is a generalization to three dimensions of Ampère’s hypothesis of molecular currents. A dynamic equation generalized to the inertial regime is obtained. It is shown how both the usual gyromagnetic relation and the well-known Landau–Lifshitz–Gilbert equation are recovered in the kinetic limit, that is, for time scales longer than the rela...

Physical Review B, 2008

A mesoscopic description of spin-transfer effect is proposed, based on the spin-injection mechani... more A mesoscopic description of spin-transfer effect is proposed, based on the spin-injection mechanism occurring at the junction with a ferromagnet. The effect of spin-injection is to modify locally, in the ferromagnetic configuration space, the density of magnetic moments. The corresponding gradient leads to a current-dependent diffusion process of the magnetization. In order to describe this effect, the dynamics of the magnetization of a ferromagnetic single domain is reconsidered in the framework of the thermokinetic theory of mesoscopic systems. Assuming an Onsager crosscoefficient that couples the currents, it is shown that spin-dependent electric transport leads to a correction of the Landau-Lifshitz-Gilbert equation of the ferromagnetic order parameter with supplementary diffusion terms. The consequence of spin-injection in terms of activation process of the ferromagnet is deduced, and the expressions of the effective energy barrier and of the critical current are derived. Magnetic fluctuations are calculated: the correction to the fluctuations is similar to that predicted for the activation. These predictions are consistent with the measurements of spin-transfer obtained in the activation regime and for ferromagnetic resonance under spin-injection.