Direct observation of the magnetic anisotropy of an Fe(II) spin crossover molecular thin film

In this work, we provide clear evidence of magnetic anisotropy in the local orbital moment of a molecular thin film based on the SCO complex [Fe(H2B(pz)(2))(2)(bipy)] (pz = pyrazol-1-yl, bipy = 2,2 & PRIME;-bipyridine). Field dependent x-ray magnetic circular dichroism measurements indicate that the magnetic easy axis for the orbital moment is along the surface normal direction. Along with the presence of a critical field, our observation points to the existence of an anisotropic energy barrier in the high-spin state. The estimated nonzero coupling constant of & SIM;2.47 x 10(-5) eV molecule(-1) indicates that the observed magnetocrystalline anisotropy is mostly due to spin-orbit coupling. The spin- and orbital-component anisotropies are determined to be 30.9 and 5.04 meV molecule(-1), respectively. Furthermore, the estimated g factor in the range of 2.2-2.45 is consistent with the expected values. This work has paved the way for an understanding of the spin-state-switching mechanism in the presence of magnetic perturbations.