Circularly polarized magnetic field generated by two microfabricated crossed coplanar waveguides

We generate a circularly polarized (CP) magnetic field using two crossed coplanar waveguides (TCCWs). By using the CP field, we selectively excite a ferromagnetic resonance between positively and negatively magnetized Co/Ni multilayers. The CP field arises from a superposition of Ampere fields generated by microwaves orthogonally propagating along the crossed arms of the TCCWs. The polarity of the magnetic field can be tuned continuously from circular to linear by exploiting a phase delay between the orthogonal microwaves. From a local measurement of the magneto-optical Kerr effect, we also find that the ellipticity of the CP field is distributed over the intersection of the TCCWs. These results indicate that TCCWs have great potential as CP-field generators that can be integrated into micron-scale electrical devices.