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Fe8 high-spin molecules exhibit quantum spin tunneling at very low temperatures. Eight Fe3+ ions are sixfold coordinated and magnetically coupled through oxygen bridges. The net magnetization (MS=20 μB per molecule) results from competing antiferromagnetic interactions between the various Fe3+ ions (S=5/2). Because of the structural anisotropy of these molecules, the magnetization curve presents a hysteresis loop with staircases below 2 K. The staircases of the hysteresis loop are due to the quantum spin tunneling, which is temperature dependent for 400 mK3He-4He dilution refrigerator. This device, that takes advantage of the thermodynamic particularities of the 3He-4He mix, let us obtain x-ray magnetic circular dichroism (XMCD) spectra at 300 mK for this molecule. It has been possible to register an XMCD remnant signal, without magnetic field applied, at the iron L2,3 edges. XMCD coupled with ligand field multiplet calculations has allowed to determine the spin and orbit contributions to the magnetization of the Fe3+ ions. [ABSTRACT FROM AUTHOR]

The article discusses a study that investigates the hysteretic behavior in vacuum deposited submonolayer of single ion magnets sublimated on pyrolytic graphite with the help of X-ray absorption spectroscopy and X-ray magnetic circular dichroism. Topics discussed include field dependence of the magnetization in central lanthanide ion at low temperature, integration of organic materials into spintronic devices and remanent magnetization of single ion magnets.