The Magnetic Properties of Manganese(II) Phthalocyanine. II

Abstract

Abstract The magnetic susceptibilities of manganese(II) phthalocyanine (PcMn) have been measured in the paramagnetic region between 13.8 and 280 K. The deviation from the Curie-Weiss law was found at a moderately high temperature (about 70 K), and the Weiss constant was obtained as 23 K. Comparing the ratio of Tc to θ (0.37) with that of the 2- or 3-dimensional lattice, the data were analysed on the basis of the ferro-magnetic linearchain model. The magnitude of the intra-chain interaction (J) was deduced as 5.64k by comparison with Fisher’s classical form of the theory of the ferromagnetic Heisenberg chain. We have also measured the magnetic susceptibilities of cobalt(II) phthalocyanine (PcCo) and of copper(II) phthalocyanine (PcCu), which are isomorphous with manganese(II) phthalocyanine, from 1.8 to 77 K. In PcCo, a broad maximum has been observed, and the data were analysed in terms of the theory of the antiferromagnetic Ising-chain model. On the other hand, PcCu obeyed the Curie law down to 1.8 K. A qualitative explanation of the exchange interactions in PcMn, PcCo, and PcCu was presented on the basis of their electronic states.