Electron spin resonance spectra of copper phthalocyanine doped with alkaline metals (AxCuPc) have been investigated. The temperature dependence of ESR spectra indicates the ferromagnetic behavior. The Curie-Weiss temperature varies from 30K to 115K depending on the stoichiometry x of samples. Some particles of polycrystalline samples were attracted to a weak magnet at temperature slightly higher than 77K. The observed magnetism is caused by unpaired pi-electrons of phthalocyanine anions on the Eg doubly degenerated molecular orbital. The observed ferromagnetism can be understood within the framework of the McConnell-2 model proposed for organic ferromagnetic charge-transfer complexes. The high-temperature magnetism in AxCuPc is considered to be a result of the Zener mechanism of double exchange between phthalocyanine molecular anions of different valence.
@article{arxiv.cond-mat/0504354,
title = {High Temperature Molecular Magnetism Caused by pi-electrons: Copper Phthalocyanine Doped with Alkaline Metals},
author = {E. G. Sharoyan and A. S. Manukyan},
journal= {arXiv preprint arXiv:cond-mat/0504354},
year = {2007}
}
Comments
6 pages, 5 figures. submitted to: Journal of Porphyrins and Phthalocyanines