Contribution of Degenerate Molecular Orbitals to Molecular Orbital Angular Momentum in Molecular Magnet Fe(Pc)(CN)₂

Abstract

We measured the static magnetic susceptibility and the electron spin resonance of the Fe(Pc)(CN)₂ complexes, and investigated the molecular magnetism of the unit Fe(Pc)(CN)₂. The magnetic susceptibility shows a highly anisotropic Curie behavior. Based on the electron spin resonance, we found a highly anisotropic g-value (g₁=3.62, g₂=1.11, and g₃=0.52) in the molecular unit Fe(Pc)(CN)₂. This anisotropy is caused by the molecular orbital angular momentum in the degenerate next highest occupied molecular orbitals of the molecular unit Fe(Pc)(CN)₂. Since the molecular unit Fe(Pc)(CN)₂ has a unique structure with fourfold symmetry, the molecular orbital angular momentum has a finite value of l_z∼+1 and −1. The anisotropic molecular magnetism of the unit Fe(Pc)(CN)₂ contributes the highly anisotropic Curie behavior. The molecular unit Fe(Pc)(CN)₂ is a good candidate for a molecular magnet having high magnetic anisotropy.