Gadolinium-Radical Chains

Although extended ID systems comprising ferromagnetically coupled gadolinium and copper ions were obtained [46], the exchange interactions were too weak to provide significant effects and the increase of the x l product was observed only at very low temperatures. A much richer scenario was instead 

A quantitative analysis of the magnetic susceptibility was attempted using a more complex spin Hamiltonian  

The helical pitch was calculated to correspond to 0 = 0.397rt and 0.399rt for the chains with R = Et and i-Pr, respectively. The decrease in xT at low temperature is justified by the fact that adjacent Gd3+ spins are almost antiparallel in these derivatives. A much smaller pitch, 0 = 0.206rc and 0.17.5re, was estimated for R = Me and Ph, respectively x h1 agreement with the increase of the xT at low temperature. 

At lower temperatures, the standard 3D helical order with all chains having not only the same chirality but also the same phase can be established. The two magnetic phase transitions present very different features. In fact, the transition to the 

It is interesting to stress that the spin chirality observed in the gadolinium radical chains differs from the more usual one that characterizes anisotropic materials and is solely due to the significant strength of NNN interactions between lanthanide ions that are very far apart. The mechanism responsible for this interaction remains unclear and the complexity of the system has, up to now, hampered an ab initio investigation of the phenomenon. 

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