EPR Spectroscopy and Exchange Interaction Parameters in Cu(glycine)2

D.M. MARTINO; M.C.G. PASSEGGI; R. CALVO; O.R NASCIMENTO

PHYSICA B - CONDENSED MATTER

Año: 1996 vol. 225 p. 63 - 75

0921-4526

EPR measurements have been performedin single crystals of Cu(glicine)2 H2O at 9.7 and 33 GHz and at room temperatures. This orthorhombic crystal has four chemically identical but magnetically non-equivalent copper ions per unit cell. The EPR data at both microwave frequencies show two partially resolved EPR lines for some of the field directions in the ab plane, while only a single line is observed along any direction in the other two crystallographic planes. This indicates that the four copper ions are arranged in two weakly coupled and symmetric-related subsets, each involving two non-equivalent and interacting copper sites. The decoupling of the spectra leads to g1= 2.256(2), g2= 2.071(2) and g3= 2.061(2) for the principal values of the molecular g-factors. The EPR data, used in conjunction with the classical Anderson´s model and the Kubo and Tomita´theory, allow to evaluate the exchange interaction parameters between the magnetically non-equivalent copper ions. The Anderson´s model amd the observed EPR line positions data lead to  J´/k = 19(3) mK for the intersubset exchange coupling. The analysis of the angular variation of the line width in terms of the Kubo and Tomita´s theory, gives  J´/k =21(2) mK and J/k= 57(1) mK for the intersubset and intrasubset exchange couplings respectively. These values are discussed in terms of the crystal structure of the compound and compared with the results obtained by other authors.