We investigate the microwave spectroscopies of a micrometer-sized single permalloy (Py) chiral structure on coplanar waveguides (CPWs). Under an external dc magnetic field applied in a direction perpendicular to the microwave propagation, the Py chiral structure loaded on the center of the CPW signal line shows Kittel-mode ferromagnetic resonance. Contrastingly, the structure on the signal-line edge highlights two additional resonances: spin-wave resonance at a higher frequency, and unique resonance at a lower frequency of approximately 7.8 GHz. The resonance signal at 7.8 GHz originates from magnetically induced, geometry-driven resonance, although the resonance frequency does not depend on the external magnetic field. Moreover, the displacement of the Py structures on the signal line results in nonreciprocal microwave transmission, which is traced back to the edge-guide mode.

We study the magneto-optical (MO) response of permalloy/silver/bismuth (Py/Ag/Bi) trilayer samples in reference to a control Py film by means of spectroscopic generalized MO ellipsometry. The trilayer structures show enhanced MO Kerr amplitude values compared to optical multilayer calculations based upon the Py film reference measurements, especially in the near-infrared region. This indicates that the optical interference conditions accounted for in the model are not sufficient to explain the influence of the Ag/Bi bilayer in the structure. Instead, the local optical and MO properties of the Py layer itself must be modified by the presence of the Ag/Bi bilayer, which could be caused by enhanced effective spin-orbit coupling.

We investigate the ferromagnetic resonance (FMR) of a single chiral structure of a ferromagnetic metal-the magnetochiral (MCh) metamolecule. Using a strain-driven self-coiling technique, micrometer-sized MCh metamolecules of metallic permalloy (Py) are fabricated without any residual Py films. The magnetization curves of ten Py MCh metamolecules obtained by an alternating gradient magnetometer show soft magnetic behavior. In cavity FMR with a magnetic-field sweep and coplanar-waveguide (CPW) FMR with a frequency sweep, the Kittel-mode FMR of the single Py metamolecule is observed. The CPW-FMR results, which are consistent with the cavity-FMR results, bring about the effective g factor, effective magnetization, and Gilbert damping of the single metamolecule. Together with calculations using these parameters, the angle-resolved cavity FMR reveals that the magnetization in the Py MCh metamolecule is most likely to be the hollow-bar type of configuration when the external magnetic field is applied parallel to the chiral axis, although the expected magnetization state at remanence is the corkscrew type of configuration.

We have succeeded in fabricating arrays of micrometer-sized, three-dimensional chiral meta-molecule (CMM) of cobalt (Co) by using a strain-driven self-coiling technique. In the arrays, the Co CMMs were fixed on a silicon substrate and aligned in the same direction. We investigated the ferromagnetic resonance of the arrays with varying angles of an external dc magnetic field. The Co CMM arrays show isotropic resonance signals, whose resonance fields are independent of the dc field orientation with respect to the helical axis.