Electrical measurement of magnetic-field-impeded polarity switching of a   ferromagnetic vortex core
  Vortex core polarity switching in NiFe disks has been evidenced using an all-electrical rectification scheme. Both simulation and experiments yield a consistent loss of the rectified signal when driving the core at high powers near its gyrotropic resonant frequency. The frequency range over which the loss occurs grows and shifts with increasing signal power, consistent with non-linear core dynamics and periodic switching of the core polarity induced by the core attaining its critical velocity. We demonstrate that core polarity switching can be impeded by displacing the core towards the disk's edge where an increased core stiffness reduces the maximum attainable core velocity. 
Manu Sushruth, Jasper P. Fried, Abdelmadjid Anane, Stephane Xavier,   Cyrile Deranlot, Mikhail Kostylev, Vincent Cros, Peter...
cond-mat.mes-hall