Polarization Effects of the Spectral Thermal Infrared and Visible Emission from Ferromagnets

摘要

Partial circular polarization of the spectral thermal emission of an axially magnetized iron rod was measured in the spectral range from 0.25 eV to 2 eV for iron-cobalt alloys. The spectra show a maximum at low energies. With increasing photon energy the polarization decreases and changes its sign at 1.35 eV, 1.50 eV, and 1.65 eV for the alloys Fe79Co21, Fe55Co45 and Fe31Co69, respectively. The dependence of the effect on wavelength and cobalt concentration is shown. The thermal radiation emitted from a ferromagnetic sample magnetized parallel to its surface is partially linearly polarized. The spectra show a shift to higher energies for increasing cobalt concentration. Polarization decreases almost linearly with rising temperature for iron and Fe31Co69. For Fe79Co21 and Fe55Co45 the polarization shows a sharp drop at the Curie temperature, associated with the phase transition from bcc to fcc. In addition, Fe55Co45 shows a hysteresis of linear polarization for rising and falling temperature, due to the order-disorder transition at 1000 K.