ACTA

Low Frequency Raman Spectrum οf Bulk Zn_0.984Co_0.016O Crystal

W. Szuszkiewicz^a, A. Łusakowski^a, J.F. Morhange^b, Z. Gołacki^a, M. Arciszewska^a, B.B. Brodowska^a, M. Kanehisa^b, M. Klepka^a and W. Dobrowolski^a
^aInstitute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warszawa, Poland
^bInstitut des Nanosciences de Paris, UPMC, CNRS UMR 7588, 140 rue de Lourmel, 75015 Paris, France

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The influence of possible presence of Co²⁺ ion pairs in a bulk Zn_1-xCo_xO mixed crystal on the low frequency part of the Raman spectrum is discussed. Two effects can be taken into account in the theoretical considerations when analyzing the energy level scheme corresponding to Co ions. The first is a local lattice deformation in the vicinity of Co²⁺ ion due to a presence of the second ion, smaller than the host ZnO lattice cation. Such deformation creates a trigonal field, which can only slightly modify the energy levels of Co²⁺ ion. The second effect, which results from an antiferromagnetic superexchange interaction between two Co²⁺ ions is responsible for a new set of energy levels. The Raman data taken at low temperature on the sample corresponding to the composition x = 0.016 demonstrated the presence of two structures at about 6 cm^-1 and 13 cm^-1. These structures may be interpreted as electronic transitions between the ground state and the first excited state of a single Co²⁺ ion in the substitution site of ZnO lattice and as a similar transition for Co²⁺ ion pair, respectively.

DOI: 10.12693/APhysPolA.116.103
PACS numbers: 75.50.Pp, 78.30.Fs