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The depinning probability of magnetic domain walls at constrictions by current pulses depends on the external magnetic field and on the temporal shape of current pulses. We investigate the depinning of domain walls in permalloy nanowires in dependence of the rise time of a current pulse. We observe a change in the depinning probability when varying the pulse rise time and the pulse amplitude at a constant magnetic field. The experiments reveal that the current density for domain-wall depinning can be strongly reduced by current pulses with short rise times.

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Vortex cores in Landau-domain patterns are resonantly excitable by alternating magnetic fields in the subgigahertz regime. We present a highly sensitive method to detect the vortex gyration in single micrometer-sized elements spectroscopically by measuring spectra of induction voltages caused by the stray fields of a single ferromagnetic square exposed to an alternating Oersted field. A distinct change of the induction voltage is observed around the resonance frequency of the vortex core. The shape of the measured spectra deviates from Lorentzian profiles due to voltages induced by magnetic fringing fields of the exciting currents. An analytical description of the measured spectra is given. A characteristic frequency shift in external magnetic fields proves that signals detected by the induction sensor originate from the dynamically excited Landau-domain pattern. The measurements on a single square are compared with measurements on an ensemble of uniform squares.