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

New data on the ground state of impurity Ru3+ ions in the crystals of YAl3(BO3)(4) and EuAl3(BO3)(4) aluminum borates were obtained. It was shown that Ru3+ 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(perpendicular to) = 3.796, A(perpendicular to) = 43.03*10(-4) cm(-1), A(perpendicular to) = 84.86*10-4 cm(-1) in the YAl3(BO3)(4) crystal (at T = 15 K) and g(II) = 2.016, g(perpendicular to) = 3.796 in the EuAl3(BO3)(4) crystal (at T = 15 K). It is found that the value of Delta g = gII - g(perpendicular to) is an indicator of distortions of nearest environment of Ru3+ ion. The angle between the C-3 axis and the direction into nearest oxygen ion was determined. The EPR linewidth of Ru3+ ion increases with increasing temperature due to the dipole-dipole and exchange interactions with the excited states of the host lattice Ru3+ ion. (C) 2016 Elsevier B.V. All rights reserved.