Splitting of standing spin-wave modes in circular submicron ferromagnetic dot under axial symmetry violation

The spin wave dynamics in patterned magnetic nanostructures is under intensive study during the last two decades. On the one hand, this interest is generated by new physics that can be explored in such structures. On the other hand, with the development of nanolithography, patterned nanoelements and their arrays can be used in many practical applications (magnetic recording systems both as media and read-write heads, magnetic random access memory, and spin-torque oscillators just to name a few). In the present work the evolution of spin wave spectra of an array of non-interacting Permalloy submicron circular dots for the case of magnetic field deviation from the normal to the array plane have been studied by ferromagnetic resonance technique. It is shown that such symmetry violation leads to a splitting of spin-wave modes, and that the number of the split peaks depends on the mode number. A quantitative description of the observed spectra is given using a perturbation theory for small angles of field inclination from the symmetry direction. The obtained results give possibility to predict transformation of spin wave spectra depending on direction of the external magnetic field that can be important for spintronic and nanomagnetic applications.

Interfacial Structure Dependent Spin Mixing Conductance in Cobalt Thin Films

Enhancement of Gilbert damping in polycrystalline cobalt thin-film multilayers of various thicknesses, overlayered with copper or iridium, was studied in order to understand the role of local interface structure in spin pumping. X-ray diffraction indicates that cobalt films less than 6 nm thick have strong fcc(111) texture while thicker films are dominated by hcp(0001) structure. The intrinsic damping for cobalt thicknesses above 6 nm is weakly dependent on cobalt thickness for both overlayer materials, and below 6 nm the iridium overlayers show higher damping enhancement compared to copper overlayers, as expected due to spin pumping. The interfacial spin mixing conductance is significantly enhanced in structures where both cobalt and iridium have fcc(111) structure in comparison to those where the cobalt layer has subtly different hcp(0001) texture at the interface.

Probing the quality of Ni filled nanoporous alumina templates by magnetic techniques

Pulsed electrodeposition prepared porous alumina templates with Ni nanowires pore filling ranged from 1 to 100%, depending on the alumina barrier-layer thickness, were probed by continuous wave ferromagnetic resonance at room temperature. For completely filled samples, a single resonance peak was observed in the whole range of angles between the applied magnetic field and normal to the sample plane. Its position was described by Kittel formula that takes into account shape anisotropy of individual Ni wires and dipolar interactions between them. For the samples with lower pore filling the effective anisotropy field decreased and the resonance linewidth in the perpendicular configuration increased. Also a quite intense second peak was observed at lower fields for these samples. These changes are associated with reduction of pore filling percentage that can lead to decrease of dipolar interactions between nanowires and to appearance of magnetic inhomogeneities inside wires.