title: Breaking of the selection rules for optical transitions in the dielectric PrFe3(BO3)4 crystal by a praseodymium-iron exchange interaction.
abstract: We report on the emergence of new lines in the optical spectrum of the PrFe3(BO3)4 single crystal at the magnetic ordering temperature. The transitions between singlet crystal-field sublevels of Pr3+ ion with the same transformational properties, strictly forbidden for the trigonal D3 point symmetry of this ion in PrFe3(BO3)4, appear below the Néel temperature and grow in intensity as a square of the order parameter. We show that the phenomenon originates from the mixing of wave functions of different Pr3+ sublevels by the Pr-Fe exchange interaction.
authors.affiliation: Institute of Spectroscopy, Russian Academy of Sciences, 142190 Troitsk, Moscow region, Russia.
authors.forename: M N
authors.initials: MN
authors.lastname: Popova
authors.forename: T N
authors.initials: TN
authors.lastname: Stanislavchuk
authors.forename: B Z
authors.initials: BZ
authors.lastname: Malkin
authors.forename: L N
authors.initials: LN
authors.lastname: Bezmaternykh