1H NMR study of dimensionality crossover in a two-dimensional antiferromagnet

• Published in: Journal of the Korean Physical Society Vol. 81; no. 12; pp. 1269 - 1273
• Main Authors: Baek, Seung-Ho, Kim, YooJin, Jung, Duk-Young, Suh, Byoung Jin
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Physical Society 01.12.2022; Springer Nature B.V
• Subjects: Anisotropy; Antiferromagnetism; Coupling; Heisenberg theory; Interlayers; Low temperature; Magnetic permeability; Magnetic properties; Mathematical and Computational Physics; NMR; Nuclear magnetic resonance; Original Paper - Condensed Matter; Particle and Nuclear Physics; Physics; Physics and Astronomy; Spin-lattice relaxation; Statistical models; Temperature; Temperature dependence; Theoretical; Three dimensional models; Two-dimensional magnet; Dimensionality crossover; Nuclear magnetic resonance
• ISSN: 0374-4884; 1976-8524
• DOI: 10.1007/s40042-022-00663-z

We report 1 H NMR study in the two-dimensional (2D) Heisenberg antiferromagnet, C 16 H 26 Mn 2 O 9 (MnDC-6). Over a wide temperature range from 300 to ∼ 8 K, we find that the linewidth of the 1 H NMR spectrum follows the temperature dependence of the uniform magnetic susceptibility χ , and the spin-lattice relaxation rate T 1 - 1 is proportional to χ T . These NMR data show that the static and dynamic magnetic properties of the system are governed by 2D antiferromagnetic (AFM) Heisenberg interactions. Remarkably, T 1 - 1 is critically enhanced in a very narrow temperature range below ∼ 6 K undergoing a three-dimensional (3D) AFM transition at T N = 4.7 K. Based on the fact that the interlayer coupling is extremely small, and the temperature dependence of the critical enhancement of T 1 - 1 is incompatible with the 3D Heisenberg model, we argue that the rapid growth of the transverse correlation length ξ ⊥ due to a small planar anisotropy leads to the spin-dimensionality crossover from 2D Heisenberg to 2D XY-like at low temperatures close to T N . Once ξ ⊥ becomes sufficiently long, even the tiny interlayer exchange coupling could trigger the 3D AFM ordering.