Interaction of Tm³⁺ions in calcium-niobium-gallium and yttrium-aluminum garnet laser crystals

Abstract

Rare-earth iron oxides of the form RFe 2 O 4 (R = Y, Ho-Lu) show a new mechanism of ferroelectricity owing to the charge ordering of Fe ions below $330 K. To determine the physical properties of this system, the magnetic and dielectric properties of HoFe 2 O 4 and R 1Àx R 0x Fe 2 O 4 were investigated (R, R 0 : rare earths). All the materials showed dielectric constants of $1000 {10000, as reported for some other RFe 2 O 4 oxides. For HoFe 2 O 4 , magnetic ordering occurred at a temperature lower than those of RFe 2 O 4 reported thus far. On the other hand, the dielectric measurements of this material suggested the development of a correlation between polar regions at higher temperatures, which was also observed for the Sc-substituted system Lu 1Àx Sc x Fe 2 O 4 . These results encourage detailed investigations of these materials from the viewpoints of both fundamental and applied sciences, and suggest the existence of other new properties of RFe 2 O 4 .