arXiv subjects

V. Castel

Publications and source records attributed to V. Castel.

6 recordsLinked to original sources

arXiv2026

Coupling phase interference effects in a multimode cavity magnonics system

Coupling phases play a decisive yet often overlooked role in cavity magnonics, particularly in complex multimode systems. Here, we investigate phase-mediated interference effects in a cavity magnonics system comprising a four-post re-entrant microwave cavity coupled to Yttrium Iron Garnet (YIG) spheres. Using an input-output model that explicitly accounts for both internal and external coupling phases, we achieve agreement with experimental microwave transmission measurements. Our results unravel the emergence of a positionally-dependent uncoupled mode due to interference of cavity photon-magnon (internal) coupling phases. Further, we experimentally observed large nonreciprocity at the antiresonance frequencies and show that this feature arises due to the far-detuned modes' odd parity cavity photon-probe (external) coupling phase interfering with the internal coupling phases. Bridging theory, simulation and experiment, these results establish coupling-phase engineering as a key principle for accurately modeling and designing multimode cavity magnonics devices.

quant-ph↗

arXiv2022

Spin wave diffraction model for perpendicularly magnetized films

We present a near-field diffraction model for spin waves in perpendicularly magnetized films applicable in any geometries of excitation fields. This model relies on Kalinikos-Slavin formalism to express the dynamic susceptibility tensor in k-space, and calculate the diffraction patterns via inverse 2D-Fourier transform of the response functions. We show an excellent quantitative agreement between our model and MuMax3 micro-magnetic simulations on two different geometries of antennas. Our method benchmarks spin wave diffraction in perpendicularly magnetized films, and is readily applicable for future designs of magnon beamforming and interferometric devices.

cond-mat.other↗

arXiv2022

High wave vector non-reciprocal spin wave beams

We report unidirectional transmission of micron-wide spin waves beams in a 55 nm thin YIG. We downscaled a chiral coupling technique implementing Ni80Fe20 nanowires arrays with different widths and lattice spacing to study the non-reciprocal transmission of exchange spin waves down to lambda = 80 nm. A full spin wave spectroscopy analysis of these high wavevector coupled-modes shows some difficulties to characterize their propagation properties, due to both the non-monotonous field dependence of the coupling efficiency, and also the inhomogeneous stray field from the nanowires.

physics.app-ph↗

arXiv2013

Exchange magnetic field torques in YIG/Pt bilayers observed by the spin-Hall magnetoresistance

The effective field torque of an yttrium-iron-garnet film on the spin accumulation in an attached Pt film is measured by the spin-Hall magnetoresistance (SMR). As a result, the magnetization direction of a ferromagnetic insulating layer can be measured electrically. Experimental transverse and longitudinal resistances are well described by the theoretical model of SMR in terms of the direct and inverse spin-Hall effect, for different Pt thicknesses [3, 4, 8 and 35nm]. Adopting a spin-Hall angle of Pt $\theta_{SH}=0.08$, we obtain the spin diffusion length of Pt ($\lambda=1.1\pm0.3$nm) as well as the real ($G_r=(7\pm3)\times10^{14}\Omega^{-1}$m$^{-2}$) and imaginary part ($G_i=(5\pm3)\times10^{13}\Omega^{-1}$m$^{-2}$) of the spin-mixing conductance and their ratio ($G_r/G_i=16\pm4$).

cond-mat.mes-hall↗

arXiv2013

YIG thickness and frequency dependence of the spin-charge current conversion in YIG/Pt systems

We report the frequency dependence of the spin current emission in a hybrid ferrimagnetic insulator/normal metal system as function of the insulating layer thickness. The system is based on a yttrium iron garnet (YIG) film [0.2, 1, and 3 \mu m] grown by liquid-phase-epitaxy coupled with a spin current detector of platinum [6 nm]. A strong YIG thickness dependence of the efficiency of the spin pumping has been observed. The highest conversion factor \Delta V/P_{abs} has been demonstrated for the thinner YIG (1.79 and 0.55 mV/mW^{-1} at 2.5 and 10 GHz, respectively) which presents an interest for the realisation of YIG-based devices. A strong YIG thickness dependence of the efficiency of the spin pumping has been also observed and we demonstrate the threshold frequency dependence of the three-magnon splitting process.

cond-mat.mtrl-sci↗

arXiv2013

Spin-Hall Magnetoresistance in Platinum on Yttrium Iron Garnet: Dependence on platinum thickness and in-plane/out-of-plane magnetization

The occurrence of Spin-Hall Magnetoresistance (SMR) in platinum (Pt) on top of yttrium iron garnet (YIG) has been investigated, for both in-plane and out-of-plane applied magnetic fields and for different Pt thicknesses [3, 4, 8 and 35nm]. Our experiments show that the SMR signal directly depends on the in-plane and out-of-plane magnetization directions of the YIG. This confirms the theoretical description, where the SMR occurs due to the interplay of spin-orbit interaction in the Pt and spin-mixing at the YIG/Pt interface. Additionally, the sensitivity of the SMR and spin pumping signals on the YIG/Pt interface conditions is shown by comparing two different deposition techniques (e-beam evaporation and dc sputtering).

cond-mat.mes-hall↗