Magnetic properties ofα-iron(II) phthalocyanine

We report on the magnetic properties of the supramolecular compound iron(II) phthalocyanine in its $\alpha$ form. dc- and ac-susceptometry measurements and Mössbauer experiments show that the iron atoms are strongly magnetically coupled into ferromagnetic Ising chains with very weak antiferromagnetic interchain coupling. The transition to three-dimensional (3D) magnetic ordering below 10 K is hindered by the presence of impurities or other defects, by which the domain-wall arrangements along individual chains become gradually blocked/frozen, leading to a disordered 3D distribution of ferromagnetic chain segments. Below 5 K, field-cooled and zero-field-cooled magnetization measurements show strong irreversible behavior, attributed to pinning of the domain walls by the randomly distributed defects in combination with the interchain coupling. High-field magnetization experiments reveal a canted arrangement of the moments in adjacent ferromagnetic chains.