Ambient temperature single crystal triplet-state E.P.R. studies on exchange coupled Cu2+-Cu2+ pairs in zinc(II) bis[N,N-diisopropyldithiocarbamate] matrix and temperature dependent E.P.R. studies on powder samples of Cu 2 § Cu 2+ and Ag2+-Ag 2+ pairs, separated by a distance of 3.545 A, in the same host lattice are reported. In addition to the doublet spectra, we observed the triplet lines arising due to spin-spin interactions. The directions of g and Dtensors in Cu 2 +-Cu 2 § pairs vary by 42 ~ in the xz-plane. The D-tensor seems to receive its contribution both from the dipolar and pseudo-dipolar interactions. The zero-field splitting (Z.F.S.) tensor, 'D', increases linearly with decrease in temperature down to 80K. This effect is seen in both Cu2+--Cu 2+ and Ag 2 § Ag 2 § pairs: it is tentatively attributed to a crystal contraction at low temperatures. The integrated intensities of AMs = + 2 E.P.R. transitions of the triplets have been used to estimate the magnitude and sign of isotropic exchange coupling constants (2,/). The values of 23 for Cu 2 +~Cu 2 +and Ag 2 +-Ag e+ pairs are found to be 40.2cm-x and 62.5 cm-1, respectively. The interaction in both the systems has been found to be 'ferromagnetic '.
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