Magnetic resonance in iron oxide nanoparticles: quantum features and effect of size

In order to better understand the transition from quantum to classical behavior in spin system, electron magnetic resonance (EMR) is studied in suspensions of superparamagnetic magnetite nanoparticles with an average diameter of ~ 9 nm and analyzed in comparison with the results obtained in the maghemite particles of smaller size (~ 5 nm). It is shown that both types of particles demonstrate common EMR behavior, including special features such as the temperature-dependent narrow spectral component and multiple-quantum transitions. These features are common for small quantum systems and not expected in classical case. The relative intensity of these signals rapidly decreases with cooling or increase of particle size, marking gradual transition to the classical FMR behavior

Ferromagnetic resonance studies in ZnMnO dilute ferromagnetic semiconductors

We report on the ferromagnetic resonance studies on ZnMnO films grown by the pulsed-laser deposition technique. ZnMnO films were annealed in different atmospheres. The films grown and annealed in oxygen demonstrate ferromagnetic behavior at room temperature and below. However, annealing in either nitrogen or argon deteriorates the ferromagnetic response of the films. Further annealing the films in oxygen recovers the ferromagnetic response. Our results suggest that oxygen plays a major role for controlling the ferromagnetic properties in ZnMnO films

Probing plasmonic electro-magnetic environment with Eu3+

We use spontaneous emission of Eu3+ ions as a spectroscopic tool to probe modifications of optical fields in close vicinity of metal and under the conditions of the optically-induced magnetic resonance. We reveal strictly different behavior of electric and magnetic dipole emission in a simple microscope setup, and also discuss the results theoretically