Easy axis crystal field limit in trivalent lanthanide complexes: expected magnetization, susceptibility, magnetic torque and XMCD signatures

Abstract

Lanthanide complexes exhibiting marked easy axis magnetic anisotropy are the main targets to achieve highly performant Single Molecule Magnets, Pseudo Contact Shift Agents and Rotating Magnetic Refrigerants. To experimentally map the magnetic anisotropy orientation and magnitude, a growing portfolio of experimental techniques is now available, including powder and single crystal magnetometry, cantilever torque magnetometry, and X-ray Magnetic Circular Dichroism. While these methods provide complementary information, reference values for ideal systems are not always applied consistently, possibly introducing ambiguity in data interpretation. Here we present a unified and quantitative set of benchmark magnetic observables for trivalent lanthanide ions exhibiting strong easyaxis anisotropy. For each ion we report: the orientation-dependent saturation magnetization and low-temperature magnetic susceptibility; the field-dependent maximum magnetic torque signal; and the angular-and field-dependent normalized XMCD response at the M 4,5 edges. The resulting tables and figures provide a simple, ready-to-use reference framework for direct comparison with experimental measurements of lanthanide-based magnetic systems.