Electronic paramagnetic resonance or rare-earth ions Yb3+, Pr3+, Dy3+, and Nd3+ in double molybdates and tungstenates

The particulars of the EPR spectrum of magnetically concentrated crystals of double molybdates and tungstenates with a crystal structure of low symmetry were studied at liquid-helium temperatures in the frequency range 15–120GHz. The directions of the principal magnetic axes were determined and the principal values of the g tensors were obtained for all experimental crystals KYb(MoO4)2, CsPr(MoO4)2, RbDy(MoO4)2, and RbNd(WO4)2. Two non-equivalent geometric centers were found in KYb(MoO4)2 and RbDy(MoO4)2 crystals; the local axes of the centers were turned in different directions relative to the crystallographic axes a and c by 34° and 25°. The dipole-dipole interaction energy was estimated as Edd∼0.1cm−1 for KYb(MoO4)2. It was shown that the lowest states of CsPr(MoO4)2 are close-lying singlets (quasidoublet) with splitting Δ∼0.2cm−1.