Covalency induced energy scale entanglement in Pr4+ compounds

Lanthanides, which typically exist in a trivalent oxidation state, possess filled 5s and 5p orbitals which shield the 4f electrons from surrounding ligands. As a result, the 4f electrons are typically only weakly perturbed by the crystalline electric field (CEF) and the spin orbital manifolds are well-separate. However, the tetravalent lanthanides show qualitatively different behavior to their 3+ counterparts. The key ingredient is the hybridization of the central ion’s f orbital with the valence p orbitals of the ligands, which contrasts with the ionic bonding found in Ln3+ systems. This covalency affects both the single ion energy scales and the inter-ion interactions, leading to anomalous magnetic behavior. In this proposal we aim to investigate the low energy magnetic excitations in Pr4+ compounds where the poor separation of energy scales and anomalously small magnetic moment may give rise to novel quantum magnetic phenomena.

通常以三价氧化态存在的镧系元素，其具有填满的5s和5p轨道，可对4f电子形成屏蔽，使其免受周围配体的影响。因此，4f电子通常仅受到晶体电场（CEF）的微弱扰动，且自旋轨道多重态分离良好。然而，四价镧系元素的行为与其三价对应物存在本质差异。其关键成因在于中心离子的f轨道与配体价层p轨道发生杂化，这与Ln³+体系中的离子键形成鲜明对比。这种共价性同时影响单离子能量尺度与离子间相互作用，进而引发反常磁行为。在本项研究提案中，我们旨在探究Pr⁴+化合物中的低能磁激发——这类化合物因能量尺度分离不佳以及反常偏小的磁矩，可能催生新型量子磁现象。