Optical spectroscopy in CoO: Phononic, electric, and magnetic excitation spectrum within the charge-transfer gap | |
Article | |
关键词: TRANSITION-METAL OXIDES; LATTICE-DYNAMICS; COBALT OXIDE; LOW-TEMPERATURES; AC CONDUCTIVITY; MIXED CRYSTALS; SHELL-MODEL; NIO; MNO; HEAT; | |
DOI : 10.1103/PhysRevB.78.245103 | |
来源: SCIE |
【 摘 要 】
The reflectivity of single-crystalline CoO has been studied by optical spectroscopy for wave numbers ranging from 100 to 28 000 cm(-1) and for temperatures 8 < T < 325 K. A splitting of the cubic IR-active phonon mode on passing the antiferromagnetic phase transition at T-N=289 K has been observed. At low temperatures the splitting amounts to 15.0 cm(-1). In addition, we studied the splitting of the cubic crystal-field ground state of the Co2+ ions due to spin-orbit coupling, a tetragonal crystal field, and exchange interaction. Below T-N, magnetic-dipole transitions between the exchange-split levels are identified, and the energy-level scheme can be well described with a spin-orbit coupling lambda=151.1 cm(-1), an exchange constant J=17.5 cm(-1), and a tetragonal crystal-field parameter D=-47.8 cm(-1). Already in the paramagnetic state electric-quadrupole transitions between the spin-orbit split level have been observed. At high frequencies, two electronic levels of the crystal-field-split d manifold were identified at 8 000 and 18 500 cm(-1).
【 授权许可】
Free