Room-temperature ferrimagnetism and size-modulated electronic structures in two-dimensional cluster-based metal-organic frameworks.

Cluster-assembled materials have attracted particular attention for their complex hierarchical structures and unique properties. However, the majority of cluster-based assemblies developed so far are either non-magnetic or only exhibit magnetic ordering with a relatively low Curie temperature, limiting their applications in spintronics. Thus, two-dimensional (2D) cluster-assembled materials with room-temperature magnetism remain highly desirable. For this purpose, based on first principles calculations, we design a series of thermodynamically stable 2D cluster-based metal-organic frameworks (MOFs) Fe_n-(pyz) (n=1–6) by utilizing Fe_n metal clusters as nodes and nitrogen-containing pyrazine ligands as organic linkers. These 2D cluster-based MOFs exhibit robust ferrimagnetic ordering due to the strong d–p direct exchange interaction between d-electron spin of Fe_n (n=1–6) clusters and charge transfer-induced p-electron spin of pyrazine ligands. In particular, the ferrimagnetic Curie temperatures are well above room temperature (up to 836 K). Additionally, altering the size of Fe_n clusters in Fe_n-(pyz) (n=1–6) MOFs results in diverse functional spintronic properties, including bipolar magnetic semiconductors, half semiconductors and Dirac half metals. Moreover, these 2D assembled MOFs possess sizable magnetic anisotropy energies, up to 9.16 meV per formula. [ABSTRACT FROM AUTHOR]