An observation of further splitting of the new fine-structure in magneto-optical spectra of CuO

Regarding CuO first in 1998 (Masumi et al., J. Phys. Sec. Japan 67 (1998) 6 7), we reported an observation of the new fine structures near the optical absorption edge below 90 K. They consist of two sharp peaks A and B at E-A = 1.57511 eV and E-B = 1.58097eV, respectively, at T = 7 K. Two peaks emerg e only below 90K and their integrated intensity remarkably grows below 90 a nd 60 K. Here, we have started a magneto-optical study to seek further natu res of these fine structures in the absorption edge of CuO by applying high magnetic fields up to B = 25T with a resolution of deltaE = 1.24 meV, Delt av = 1 cm(-1). Peaks A and B exhibit rather little variations up to 10 T. A bove 12 T, however, there starts to emerge a potential splitting in the pea k A, whereas peak B simply indicates a broadening. Finally, we clearly reco gnize new finer structures due to splitting in peak A at B = 25 T. These re sults reveal a possibility of an existence of further peculiar magnetic cha racters in CuO even at lower temperature side besides the antiferromagnetic transitions at T-N1 = 213 K and T-N2 = 230 K. (C) 2001 Elsevier Science B. V. All rights reserved.