EPR study of the low-spin state of Ru3+in the YAl3(BO3)4 and EuAl3(BO3)4 aluminum borates

Abstract New data on the ground state of impurity Ru 3+ ions in the crystals of YAl 3 (BO 3 ) 4 and EuAl 3 (BO 3 ) 4 aluminum borates were obtained. It was shown that Ru 3+ ion replaces trivalent rare-earth ions without breaking the symmetry of the site. The crystal field acting on 4d 5 ions forms an EPR spectrum, which is described by the spin Hamiltonian with S =1/2. The spin-Hamiltonian parameters determined are equal to g II =1.963, g ⊥ =3.796, A II =43.03*10 −4  cm −1 , A ⊥ =84.86*10 −4  cm −1 in the YAl 3 (BO 3 ) 4 crystal (at Т =15 K) and g II =2.016, g ⊥ =3.796 in the EuAl 3 (BO 3 ) 4 crystal (at Т =15 K). It is found that the value of ∆ g = g II - g ⊥ is an indicator of distortions of nearest environment of Ru 3+ ion. The angle between the C 3 axis and the direction into nearest oxygen ion was determined. The EPR linewidth of Ru 3+ ion increases with increasing temperature due to the dipole-dipole and exchange interactions with the excited states of the host lattice Ru 3+ ion.