Spin Chains with Highly Quantum Character through Strong Covalency in Ca 3 CrN 3

• Published in: Journal of the American Chemical Society 2025-01
• Main Authors: Kautzsch, Linus, Georgescu, Alexandru B, Yuan, Lin-Ding, Taddei, Keith M, Reilly, Aiden, Seshadri, Ram, Rondinelli, James M, Wilson, Stephen D
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.4c11629

The insulating transition metal nitride Ca CrN consists of sheets of triangular [CrN ] units with symmetry that are connected via quasi-1D zigzag chains. Due to strong covalency between Cr and N, Cr ions are unusually low-spin, and = 1/2. Magnetic susceptibility measurements reveal dominant quasi-1D spin correlations with very large nearest-neighbor antiferromagnetic exchange = 340 K and yet no sign of magnetic order down to = 0.1 K. Density functional theory calculations are used to model the local electronic structure and the magnetic interactions, supporting the low-spin assignment of Cr that is driven by strong π donation from the nitride ligands. The surprising failure of interchain exchange to drive long-range magnetic order is accounted for by the complex connectivity of the spin chain pairs that further frustrates order. Our combined results establish Ca CrN as a nearly ideal manifestation of a quantum spin chain whose dynamics remain unquenched down to extraordinarily low temperatures despite strong near-neighbor exchange coupling.