Recent progress in magneto-optics and research on its application

摘要

Various kinds of magneto-optical properties are investigated in rare earth orthochromites. From an analysis of Cr{sup}(3+) exciton absorption in RcrO{sub}3 (R= Tb, Dy, and Ho), it is unferred that these compounds exhibit an anomalous spin-reorientation in a magnetic field along the b axis, where the weak ferromagnetic moment of the Cr{sup}(3+) spins rotates in the ac plane perpendicular to the b axis. In these compounds, when the R{sup}(3+) spin configuration is disordered, an anomalous satellite band appears on the lower-energy side of the Cr{sup}(3+) exciton absorption, which is associated with the breakdown of the k= 0 selection rule due to the disorder of the R{sup}(3+) spin configuration. In YbCrO{sub}3, various kinds of cooperative excitations, such as a Cr{sup}(3+) exciton coupled with an Yb{sup}(3+) magnon and a Cr{sup}(3+) - Yb{sup}(3+) exciton molecule, which are induced by the antisymmetric exchange interaction between the Cr{sup}(3+) and Yb{sup}(3+) spins, appear in the visible region. The propagation of these cooperative excitations depends strongly on the spin structure and the external magnetic field. In ErCrO{sub}3, a photo-induced spin-reorientation takes place within 50μs after the photo-irradiation corresponding to the 4{sup left}A{sub}(2g)→2{sup left}E{sub}g transition of C{sup}(3+), and it returns to the initial spin configuration in about 400 ms. This phenomenon is detected in the time-resolved Er{sup}(3+) absorption spectra corresponding to the 4{sup left}I{sub}(15/2)→4{sup left}I{sub}(9/2) transition. Finally, we briefly review the recent frontier research on applications developed mainly in Japan.