Magnetic droplet solitons in orthogonal nano-contact spin torque oscillators

We study microwave signal generation as a function of drive current and applied perpendicular magnetic field in nano-contact spin torque oscillators (NC-STOs) based on orthogonal (pseudo) spin valves where the Co fixed layer has strong easy-plane anisotropy, and the [Co/Ni] free layer has a strong perpendicular magnetic anisotropy. The orthogonal NC-STOs exhibit a dramatic transition from the conventional ferromagnetic resonance-like spin wave mode to a magnetic droplet soliton mode. In particular, the field and current dependence of the droplet soliton near threshold are discussed. Near threshold the droplet soliton undergoes complex dynamics that include mode hopping, as evident in the experimental frequency domain and magnetoresistance response

A new phenomenon on the surface of FINEMET alloy

This paper is devoted to the analysis of quadratic magneto-optical effects (QMOKE) newly observed at the surface of FINEMET-type Fe73.5Si13.5Nb3Cu1B9 ribbons annealed at temperatures of 733 K and 743 K. A strongly inhomogeneous surface microstructure detected by grazing incident X-ray diffraction (GIXRD), scanning (SEM) and transmission (TEM) electron microscopy is responsible for amplitude and sign changes of the QMOKE in different sample places. Signals in saturation determined by an 8-directional method confirm the prevailing influence of M L M T contributions at some places of a surface and of M2L−M2T at other ones, where M L and M T are in-plane longitudinal and transversal magnetization components. This behavior is explained by random orientation of nanocrystals and/or clusters of the nanometer size (typically units of nm) in the surface layers. The maximal QMOKE magnitude in saturation reaches at some places as much as 0.2 mrad, which is approximately three times lower than the highest contribution observed in Co2FeSi Heusler compounds.Web of Science2641352134