Vieru Veacheslav, Iwahara Naoya, Ungur Liviu, Chibotaru Liviu F
Theory of Nanomaterials Group, Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium.
Sci Rep. 2016 Apr 18;6:24046. doi: 10.1038/srep24046.
Combining strong magnetic anisotropy with strong exchange interaction is a long standing goal in the design of quantum magnets. The lanthanide complexes, while exhibiting a very strong ionic anisotropy, usually display a weak exchange coupling, amounting to only a few wavenumbers. Recently, an isostructural series of mixed (Ln = Gd, Tb, Dy, Ho, Er) have been reported, in which the exchange splitting is estimated to reach hundreds wavenumbers. The microscopic mechanism governing the unusual exchange interaction in these compounds is revealed here by combining detailed modeling with density-functional theory and ab initio calculations. We find it to be basically kinetic and highly complex, involving non-negligible contributions up to seventh power of total angular momentum of each lanthanide site. The performed analysis also elucidates the origin of magnetization blocking in these compounds. Contrary to general expectations the latter is not always favored by strong exchange interaction.
将强磁各向异性与强交换相互作用相结合是量子磁体设计中一个长期存在的目标。镧系配合物虽然表现出非常强的离子各向异性，但通常显示出较弱的交换耦合，仅为几个波数。最近，已经报道了一系列同构的混合（Ln = Gd、Tb、Dy、Ho、Er），其中交换分裂估计达到数百个波数。本文通过结合详细的建模与密度泛函理论和从头计算，揭示了这些化合物中异常交换相互作用的微观机制。我们发现它基本上是动力学的且高度复杂，涉及每个镧系位点总角动量七次方的不可忽略的贡献。所进行的分析还阐明了这些化合物中磁化阻塞的起源。与一般预期相反，后者并不总是受到强交换相互作用的青睐。
