ANTIFERROMAGNETIC-RESONANCE IN BI2CUO4

Magnetic resonance of the low-frequency spin-wave branch in the Bi2CuO 4 antiferromagnet with an easy-plane anisotropy has been studied. Angu lar, frequency, and temperature dependences of the position and width of the antiferromagnetic resonance (AFMR) line have been measured. Our measurements combined with earlier data [H. Ochta, K. Yoshida, T. Mat suya, T. Nanba, M. Motokawa, K. Yamada, Y. Endon, and S. Hosoya, J. Ph ys. Sec. Jpn. 61, 2921 (1992); E. W. Ong, G. H. Kwei, R. A. Robinson, B. L. Ramakrishna, and R. B. von Dreele, Phys. Rev. B 42, 4255 (1990)] have allowed us to determine anisotropy constants of this material an d to account for the unusual character of its static susceptibility an isotropy. The AFMR line shifts to the high-field side and broadens in a temperature range of 10-15 K, and the cause of this has remained unc lear. In the low-temperature range the line shows a hysteresis corresp onding to a static field magnitude several times as large as the spin- flop field. The position and width of the AFMR line depend sensitively on the sample preparation technique. (C) 1998 American Institute of P hysics.