Evidence for the magnetic Franck-Condon effect in a system of an interstitial magnetic impurity in an antiferromagnetic matrix : Cr(3+) in GdAlO3

Abstract

Absorption and emission measurements of the 4A2-2E transitions of Cr3+ in GdAlO3 at T ¡Ü4.2 K, in magnetic fields up to 6 T parallel to the easy axis, are consistent with a magnetic Franck-Condon principle for which the energy difference between the absorption and emission lines arises mainly from the spin relaxation, rather than the neighboring ion space coordinates around the impurity. The Cr-Gd exchange-coupling const. changes with the applied magnetic field from J = 2.1 cm-1 at H = 0 to Jsat = 1.46 cm-1 at high field.