arXiv subjects

N. Bardou

Publications and source records attributed to N. Bardou.

3 recordsLinked to original sources

arXiv2024

Spectroscopy of the spin waves of a synthetic antiferromagnet grown on a piezoelectric substrate

Efficient coupling between magnons and phonons requires material platforms that contain magnetic multilayers with versatile high-frequency properties grown on piezoelectric substrates with large electromechanical coupling coefficients. One of these systems is the CoFeB/Ru/CoFeB Synthetic antiferromagnet grown on Lithium Niobate substrate. We investigate its microwave magnetic properties using a combination of ferromagnetic resonance and propagating spin wave spectroscopy, from which we extract the dispersion relation of the acoustic branch of spin waves. The frequency and the linewidth of this spin wave resonance, its field dependence and its dispersion relation indicate that the magnetic properties are as good as when grown on standard non-piezoelectric substrates, as well as being in line with theory. This new material platform opens opportunities to extend microwave acousto-magnonics beyond the use of single layer magnets.

cond-mat.mtrl-sci↗

arXiv2024

Unidirectional spin waves measured using propagating spin wave spectroscopy

The dispersion relation of spin waves can vary monotonically about the center of the Brillouin zone, allowing zero-momentum wavepackets to flow unidirectionally, which is of interest for applications. Techniques such as propagating spin wave spectroscopy are inoperative in such cases because of the difficulty to identify the spin wave wavevector at a particular frequency within a spectrum. Here we present a method to analyse this case and apply it to acoustic spin waves in a synthetic antiferromagnet in the scissors state, in which we confirm that propagation parallel to the applied fields is unidirectional. Interestingly, we find that in this unidirectional situation, the phase accumulated by the spin waves propagating between two antenna is not proportional to the antenna spacing. It is also a function of the two other lengths of the problem: the antenna width and the spin wave decay length. Accounting for them is required to avoid wavevector errors in the dispersion relations.

cond-mat.mtrl-sci↗

arXiv2014

Mapping the radiative and the apparent non-radiative local density of states in the near field of a metallic nanoantenna

We present a novel method to extract the various contributions to the photonic local density of states from near-field fluorescence maps. The approach is based on the simultaneous mapping of the fluorescence intensity and decay rate, and on the rigorous application of the reciprocity theorem. It allows us to separate the contributions of the radiative and the apparent non-radiative local density of states to the change in the decay rate. The apparent non-radiative contribution accounts for losses due to radiation out of the detection solid angle and to absorption in the environment. Data analysis relies on a new analytical calculation, and does not require the use of numerical simulations. One of the most relevant applications of the method is the characterization of nanostructures aimed at maximizing the number of photons emitted in the detection solid angle, which is a crucial issue in modern nanophotonics.

physics.optics↗