Electromagnon Resonance at Room Temperature with Gigantic Magnetochromism

Abstract

Elementary excitation characteristic of the magnetoelectric (ME) multiferroics is a magnon endowed with the electric activity, which is referred to as electromagnon. The electromagnon resonance mediated by the bilinear exchange coupling potentially exhibits the strong terahertz light-matter interaction with novel optical properties different from the conventional magnon excitation. Here we report the robust electromagnon resonance on the helimagnetic Y-type hexaferrites in a wide temperature range including room temperature. Furthermore, the efficient magnetic-field controls of the electromagnon are demonstrated on the flexible spin structure of these compounds, leading to the generation/annihilation of the resonance as well as the large resonance energy shift. These terahertz characteristics of the electromagnon exemplify the versatile magneto-optical functionality driven by the ME coupling in the multiferroics, paving a way for possible terahertz applications as well as terahertz control of a magnetic state of matter.

Floating zone furnace equipped with a high power laser of 1 kW composed of five smart beams

“…Y-type hexaferrite single crystals have been conventionally grown by a flux method [9] because these materials show incongruent melting. Nevertheless, we have succeeded in growing a large single crystal [10][11][12] of Y-type hexaferrite Ba2Co2Fe12O22, known as a multiferroic compound of spin origin, by using the present LFZ. We adopt the following growth conditions; 10 atmospheres of oxygen gas atmosphere and a growth rate of 1mm/h.…”