Observation of 63,65Cu and 209Bi nuclear resonance in antiferromagnetic Bi2CuO4

A complex spin-echo spectrum of 63,65Cu and 209Bi has been observed in various ceramic and single-crystal samples of Bi2CuO4 in antiferromagnetic phase at a temperature of 4.2 K. The spectrum consists of 63,65Cu AFNR and 209Bi NQR with a complex structure of resonance lines due to magnetic inequivalency of Bi atoms and a large asymmetry parameter. The Cu AFNR is characterized by the internal field Hint∼99 kOe at Cu nuclei and by the quadrupole frequency 63νQ ∼10 MHz. The obtained value of Hint corresponds to 0.82 μB for the Cu2+ magnetic moment. It is shown that the low limit of the internal field at 209Bi nuclei is approximately 4.3 kOe and consists of the dipolar field Hdip=0.85 kOe and the hyperfine field Hhf which essentially exceeds Hdip. The occurrence of Hhf at 209Bi nuclei shows that Bi3+ anions take part in the superexchange interaction between Cu atoms along the Cu-O-Bi-O-Cu bonds. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)