Cluster of four superexchange‐coupled Cu2+ ions in copper‐doped triglycine fluoroberyllate. A theoretical interpretation of the EPR spectrum

Abstract

AbstractThe unusual EPR spectrum of copper‐doped triglycine fluoroberyllate is shown to originate in large complcx molecules of the hypothetical formula [Cu2+·(NH2CH2COO−)2·H2BeF4]4, built into the distorted host lattice. Superexchange couplings of Cu2+ ions in the cluster through CuFBeFCu paths are discussed. The isotropic superexchange interactions split the 16‐fold degenerate ground crystal state of the four Cu2+ ions into multiplets the further splitting of which, originated by anisotropic interactions, can be described in terms of effective spin Hamiltonians with S = 2 and 1. The observed spectrum is attributed to transitions within the quintet and one of the triplets. By second‐order perturbation procedure, the phenomenological parameters of the effective spin Hamiltonians are expressed in terms of parameters directly describing anisotropic as well as isotropic superexchange interactions in the cluster. The magnitudes of these interactions are thus determined from experimental data.