Spectroscopy of the parametric magnons excited by 4-wave process

Using a Magnetic Resonace Force Microscope, we have performed ferromagnetic resonance (FMR) spectroscopy on parametric magnons created by 4-wave process. This is achieved by measuring the differential response to a small source modulation superimposed to a constant excitation power that drives the dynamics in the saturation regime of the transverse component. By sweeping the applied field, we observe abrupt readjustement of the total number of magnons each time the excitation coincides with a parametric mode. This gives rise to ultra-narrow peaks whose linewith is lower than $5~10^{-6}$ of the applied field.Comment: 4 page

Influence of the magnetic tip in ferromagnetic resonance force microscopy

We compare mechanically detected ferromagnetic resonance spectra for different separations h between the magnetic tip and sample surface. When the bias field generated by the tip is smaller than a few hundred gauss, the prominent changes are shifts of the entire spectrum (without line shape distortions) to higher frequency as h decreases. These results are in agreement with the Damon and Eshbach model for spin waves propagating in a potential perturbed by the additional field of the probe magnet. It is used to predict the spatial resolution limit for magnetostatic modes bounded by the stray field of the tip. The answer is ∼4μm for yttrium iron garnet. © 2002 American Institute of Physics

Measurement of the ferromagnetic relaxation in a micron-size sample

It is shown that magnetic-resonance force microscopy can provide direct measurements of both the longitudinal and the transverse relaxation rates in a micron-size ferromagnetic sample. As a demonstration, we have applied the technique to a single crystal disk of yttrium iron garnet. Separation between the individual relaxation channels is achieved through a comparison of the results obtained by three different experiments: resonance linewidth measurements, source and frequency modulation, and quantitative measurement of the longitudinal magnetization

Quantitative measurement of the ferromagnetic resonance signal by force detection

The change of longitudinal magnetization which is associated with the resonant absorption of microwave power in a ferromagnetic crystal was studied. Magnetic resonance force microscope was used. It was found that the ferromagnetic resonance can be studied by analyzing the dipolar force exterted between a disk and a cylindrical probe magnet

Direct measurement of the spin-lattice relaxation in a ferromagnet

We propose to use ferromagnetic resonance force microscopy to measure the dissipative term that enters in the equation of motion for the magnetization vector. The experiments were carried out at microwave frequencies on a micron-size single crystal disk of yttrium iron garnet. We compare the results obtained by resonance linewidth measurements and quantitative measurement of the longitudinal magnetization. © 2003 Elsevier B.V. All rights reserved

Mechanical detection of ferromagnetic resonance spectrum in a normally magnetized yttrium-iron-garnet disk

The ferromagnetic resonance spectrum of a normally magnetized yttrium-iron-garnet disk, with thickness of 4.75 μm and radius of 80 μm, is measured at room temperature both by magnetic resonance force microscopy and by standard detection of the microwave susceptibility. The comparison indicates that magnetic resonance force microscopy represents one of the most potent means of obtaining the complete ferromagnetic resonance spectra of micron-size samples. In the weak coupling regime, the measured data can be quantitatively understood within the framework of the Damon and Eshbach model. © 2002 American Institute of Physics

Ferromagnetic resonance spectroscopy of parametric magnons excited by a four-wave process

Using a magnetic resonance force microscope, we have performed ferromagnetic resonance spectroscopy of the parametric magnons created by a four-wave process. This is achieved by measuring the differential response to a small amplitude modulation superimposed to a large constant excitation power that drives the dynamics of the uniform mode in the saturation regime. By sweeping the applied field, we observe an abrupt readjustment of the total number of magnons each time the excitation coincides with a parametric mode. This gives rise to ultranarrow peaks whose linewidth is lower than 5× 10-6 of the applied field. © 2007 The American Physical Society

Stochastic model for differential Mueller matrix of stationary and non-stationary turbid media

International audienceWe show the existence of different regimes in spatial evolution of depolarization in turbid media characterized by a diagonal Mueller matrix (pure depolarizer). Experimental results previously published already established the existence of a first regime, where the depolarization follows a parabolic law with the thickness of stationary medium traveled by light. New experiments first confirm the existence of a second regime, which we have previously demonstrated, where the depolarization follows a linear law on a large scale. They also confirm the existence of much more complex evolution laws even under small-scale approximation. A stochastic approach is proposed to model the phenomenon. It perfectly describes all these different experimental results and allows us to analyze the behavior of the polarization in the case of solid or liquid scattering media. The influence of themeasurement setup is also analyzed