Enhanced Curie Temperature of Two-Dimensional Cr(II) Aromatic Heterocyclic Metal-Organic Framework Magnets via Strengthened Orbital Hybridization.

Abstract

Two-dimensional (2D) metal-organic frameworks (MOFs) with room-temperature magnetism are highly desirable but challenging due to the weak superexchange interaction between metal atoms. For this purpose, strengthening the hybridization between metal ion and organic linkage presents an experiment-feasible chemical solution to enhance the Curie temperature. Here, we report three 2D Cr(II) aromatic heterocyclic MOF magnets with enhanced Curie temperature by bridging Cr(II) ions with pyrazine, 1,4-diphosphinine, and 1,4-diarsenin linkers, i.e., Cr(pyz)2, Cr(diphos)2, and Cr(diarse)2, and using first-principles calculations. Our results show that Cr(pyz)2, Cr(diphos)2, and Cr(diarse)2 are ferrimagnetic semiconductors. In particular, the Curie temperature of Cr(pyz)2 is estimated to be about 344 K and could be enhanced to 512 and 437 K in Cr(diphos)2 and Cr(diarse)2 by strengthening the hybridization between Cr ions and organic linkers via d-π* direct exchange interaction. This study presents a prototype to obtain room-temperature magnetism in 2D Cr(II)-based MOF magnets for nanoscale spintronics applications.