Development of Organic Ferromagnets Based on Transition Metal Phthalocyanines

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A series of organic ferromagnetic materials based on transition metal phthalocyanines (MPcs) doped by alkaline metals are synthesized and the magnetic properties and the crystal structures are investigated. All the samples of MPc, where M=Mn, Fe, Co, Ni, doped by sodium or potassium, show ferromagnetic behavior at room temperature. X-ray diffraction patterns and transmission electron microscopy images suggest that the MPc molecules form three-dimensional random networks in the alkaline metal doped MPc samples. Three-dimensional ferromagnetic interactions between transition metal ions in connected MPc molecules via delocalized π-electrons are proposed to explain the high Curie temperature well above room temperature. We also synthesized the MPc polymers and studied its structure and magnetic properties. Ferromagnetic behavior is also observed in the magnetization measurements at room temperature. These experimental results could be a clue to finding high Curie temperature ferromagnetism in organic materials.