Non-conventional resonant behavior of an unconfined magnetic domain wall in a permalloy strip

Abstract

The resonant dynamic of a magnetic domain wall in a permalloy microstrip has been investigated using an innovative experimental setup that enables a simultaneous measurement of the ferromagnetic resonance and the magnetoresistance. The resonance frequency associated with the presence of the magnetic domain wall increases linearly with the external magnetic field in the range of fields where the domain wall is present in the microstrip. This linear behavior is unusual in a domain wall and not related to the standard resonant modes of a magnetic domain wall, such as breathing, twisting, or translational modes. The slope of this linear dependency is 1.38 GHz/mT, which is an incredibly large value and allows the detection of very small changes in the external magnetic field. This linear behavior opens a path for developing a highly tunable radio frequency oscillator or a magnetic sensing device where the presence of an external field is detected via small variations in the resonant frequency of the domain wall.