Paramagnetic Anisotropy, Low Temperature Magnetization, and Electronic Structure of Iron(II) Phthalocyanine

• Published in: The Journal of chemical physics 1970-09, Vol.53 (5), p.1643-1648
• Main Authors: Barraclough, C. G., Martin, R. L., Mitra, S., Sherwood, R. C.
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.1674237

Magnetic anisotropy, magnetization, and average magnetic susceptibility have been measured for iron (II) phthalocyanine. The anisotropy was measured from the room temperature to about 90°K, the average susceptibility from 296 to 1.57°K, and the magnetization was measured at 1.57°K for field strengths between 1100 and 15 000 Oe. The results are interpreted in terms of a B2g3 ground state with a zero-field splitting parameter D = 64 cm−1, and g‖ = g⊥ = 2.74. Iron (II) phthalocyanine is an unusual example in which a large magnetic anisotropy arises entirely from the zero-field splitting. The danger inherent in the existing method of evaluation of ligand-field parameters from the average magnetic susceptibility data has been highlighted, and the advantages of magnetic anisotropy studies in deducing the ligand-field parameters and the electronic structures are discussed. A change of about 70° of the “setting angle” between 290 and 90°K is observed in this crystal when measured with b axis vertical. It is shown that this change is not indicative of a change in the ligand-field parameters with temperature, as generally assumed previously, but depends on the temperature dependence of the ratio of principal susceptibilities.