Spin dynamics and magnetic properties

Nanomagnetic materials are widely studied for their outstanding properties in numerous area of emergent quantum technologies, such as nanoscale magnetometry, quantum metrology, information processing and communications, as well as for high-resolution magnetic resonance imaging (MRI). In the last years, hyperpolarized 13C based MRI has emerged for in vivo applications. In particular, nanodiamonds (ND) offer exciting possibilities as novel hyperpolarized probes. In this context, the team participates in the HYPERDIAMOND project, which was part of the European Union’s Horizon 2020 research and innovation program. In another research field, our recent theoretical studies and numerical simulations of the inertial regime of the magnetization could offer a major interest in the ultrafast spin dynamics for spintronic device applications.
The team's experimental techniques are electron paramagnetic resonance (X and Q-bands) and magnetometry (PPMS system) but numerical approaches such as dynamic simulation are also used.

Recent work

Inertial Dynamics Of The Magnetization

Effect of inertia  for a single spin Effect of inertia  for interacting spins Figure on the left side displays the FMR peaks obtained by numerical simulations for a single spin dynamics. The nutation peak at high frequency is the signature of inertia.
In the case of interacting spins, a new collective mode appears, called the nutation wave which has distinct properties compared to the usual spin wave. Figure on the right side displays the dispersion relation of the nutation wave (upper curve, Higgs mode with a gap at k=0) and spin wave (lower curve, gapless Goldstone mode).


 

Paramagnetic nitrogen defects in 13C-enriched nanodiamonds studied by electron paramagnetic resonance (EPR) and numerical simulation.

Paramagnetic nitrogen defects in 13C-enriched nanodiamonds


The EPR spectra (blue lines) and simulation results (orange lines) for representative ND samples with different percentages of 13C indicate the predominance of the defect (known as P1-centre) arising from a substitutional nitrogen atom with the additional electron coupled with the 14N spin-1 nucleus and the 13C spin-1/2 nuclei likely to occupy the closest crystalline sites. For relatively high density of 13C nuclei, the best simulations are obtained by adding to the signal associated with the P1-centres a broad spin-1/2 Lorentzian component, whose nature has not yet been established.