The static and dynamic properties of ring-shaped nanostructures have stimulated much interest because of their potential applications in the field of magnetoelectronic devices. In this work we present a combined magnetic force microscopy (MFM), magneto optic Kerr effect (MOKE) and both conventional and micro-focused Brillouin light scattering (BLS) study of thermal spin waves in micrometric-sized NiFe slotted rings (outer radius 1.4 micron, inner radius 0.6 micron, thickness 30nm). We measured samples with a slot angular aperture of 30° and 60° respectively as well as full rings as reference. MFM and BLS measurements have been performed as a function of the intensity of an external magnetic field applied perpendicular to the slot axis. MFM measurements allowed us to follow the evolution of the magnetization configuration from the onion to a vortex state and finally to a reversed onion state. We also observed the formation of inner vortices (i.e. vortices which are localized in a single ring’s arm) which drive the reorientation processes (Fig.1 left). We employed BLS spectroscopy in order to study the spin excitations inside the magnetic elements and, thanks to the reduced spot size of our micro-focused BLS apparatus, we were also able to extract local information on the spin wave excitations spectra of our samples focusing the light on different points of interest over a single magnetic element (Fig.1 right). Experimental results were satisfactorily reproduced by means of both static and dynamic micromagnetic simulations performed with OOMMF. This work was supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under Grant Agreement n°228673 (MAGNONICS) and by CNISM under Innesco μ-BLS project.
Magnetization configurations and spin excitations in micrometric-sized NiFe slotted rings
BISERO, Diego;
2011
Abstract
The static and dynamic properties of ring-shaped nanostructures have stimulated much interest because of their potential applications in the field of magnetoelectronic devices. In this work we present a combined magnetic force microscopy (MFM), magneto optic Kerr effect (MOKE) and both conventional and micro-focused Brillouin light scattering (BLS) study of thermal spin waves in micrometric-sized NiFe slotted rings (outer radius 1.4 micron, inner radius 0.6 micron, thickness 30nm). We measured samples with a slot angular aperture of 30° and 60° respectively as well as full rings as reference. MFM and BLS measurements have been performed as a function of the intensity of an external magnetic field applied perpendicular to the slot axis. MFM measurements allowed us to follow the evolution of the magnetization configuration from the onion to a vortex state and finally to a reversed onion state. We also observed the formation of inner vortices (i.e. vortices which are localized in a single ring’s arm) which drive the reorientation processes (Fig.1 left). We employed BLS spectroscopy in order to study the spin excitations inside the magnetic elements and, thanks to the reduced spot size of our micro-focused BLS apparatus, we were also able to extract local information on the spin wave excitations spectra of our samples focusing the light on different points of interest over a single magnetic element (Fig.1 right). Experimental results were satisfactorily reproduced by means of both static and dynamic micromagnetic simulations performed with OOMMF. This work was supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under Grant Agreement n°228673 (MAGNONICS) and by CNISM under Innesco μ-BLS project.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.