Electromagnon Resonance at Room Temperature with Gigantic Magnetochromism

Light at terahertz frequencies is seen as key to future applications, but the related technology is still at a developmental stage. In contrast to the usual magnon (magnetic collective excitation) possessing an ac magnetic response in the GHz range, magnetoelectric coupling in a multiferroic material provides a resonance with electrical activity in the coveted THz region---an $e\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}m\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}g\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n$. This study of multiferroic Y-type hexaferrites demonstrates robust electromagnon resonances and their versatile magnetic control, even at room temperature, thus providing an avenue to THz applications.