Novel magnetic and heat capacity properties of the Cr(IV) diperoxides

This study presents, to our knowledge, the first observation of long range magnetic order in a simple Cr(IV) organo-metallic complex. Magnetic susceptibility and heat capacity results are given for an Cr(IV) ethylenediamine diperoxo complex, [Cr(En)(O-2)(2)(H2O)]. H2O. For the investigated compound, the spin state of S=1 was determined from the analysis of susceptibility data above 20 K. Below this temperature the susceptibility was observed to deviate from Curie-Weiss behavior. We find evidence for long range ordering similar to ferromagnetism around 4.5 K, and the appearance of short range spin interactions at higher temperatures. The mechanism for the ferromagnetic like peak has tentatively been attributed to canted anti-ferromagnetism. Analysis of the heat capacity determined that the majority of the spin entropy is engaged at temperatures above 10 K. (C) 2000 American Institute of Physics. [S0021-8979(00)79208-5].