Spin Chains with Highly Quantum Character through Strong Covalency in Ca3CrN3

Linus Kautzsch; Alexandru B Georgescu; Lin-Ding Yuan; Keith M Taddei; Aiden Reilly; Ram Seshadri; James M Rondinelli; Stephen D Wilson

doi:10.1021/jacs.4c11629

Spin Chains with Highly Quantum Character through Strong Covalency in Ca₃CrN₃

J Am Chem Soc. 2025 Jan 21. doi: 10.1021/jacs.4c11629. Online ahead of print.

Authors

Linus Kautzsch¹, Alexandru B Georgescu^{2

3}, Lin-Ding Yuan², Keith M Taddei⁴, Aiden Reilly¹, Ram Seshadri^{1

5}, James M Rondinelli², Stephen D Wilson⁶

Affiliations

¹ Materials Department and Materials Research Laboratory, University of California, Santa Barbara, Santa Barbara, California 93106, United States.
² Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.
³ Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States.
⁴ Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
⁵ Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States.
⁶ Materials Department, University of California, Santa Barbara, Santa Barbara, California 93106, United States.

PMID: 39835709
DOI: 10.1021/jacs.4c11629

Abstract

The insulating transition metal nitride Ca₃CrN₃ consists of sheets of triangular [CrN₃]^6- units with C_2v symmetry that are connected via quasi-1D zigzag chains. Due to strong covalency between Cr and N, Cr³⁺ ions are unusually low-spin, and S = 1/2. Magnetic susceptibility measurements reveal dominant quasi-1D spin correlations with very large nearest-neighbor antiferromagnetic exchange J = 340 K and yet no sign of magnetic order down to T = 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 Cr³⁺ 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 Ca₃CrN₃ 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.