Slow spin dynamics in the hyper-honeycomb Lattice [(C2H5)3NH]2Cu2(C2O4)3 revealed by 1H NMR studies

Q. -P. Ding; C. Dissanayake; Santanu Pakhira; W. J. Newsome; F. Uribe-Romo; D. C. Johnston; Y. Nakajima; Y. Furukawa

doi:10.1103/PhysRevB.105.L100405

paper

Slow spin dynamics in the hyper-honeycomb Lattice [(C2H5)3NH]2Cu2(C2O4)3 revealed by 1H NMR studies

arXiv:2201.11243 · doi:10.1103/PhysRevB.105.L100405

Abstract

We report the results of magnetic susceptibility $χ$ and $^{1}$ H nuclear magnetic resonance (NMR) measurements on a three-dimensional hyper-honeycomb lattice compound [(C $_{2}$ H $_{5}$ ) $_{3}$ NH] $_{2}$ Cu $_{2}$ (C $_{2}$ O $_{4}$ ) $_{3}$ (CCCO). The average value of the antiferromagnetic (AFM) exchange coupling between the Cu $^{2 +}$ ( $S$ = 1/2) spins was determined to be $J$ ~ $\sim$ ~50 K from the $χ$ measurements. No long-range magnetic ordering has been observed down to $T$ = 50 mK, although NMR lines become slightly broader at low temperatures below 1 K. The broadening of the NMR spectrum observed below 1 K reveals that the Cu spin moments remain at this temperature, suggesting a non-spin-singlet ground state. The temperature and magnetic field dependence of 1/ $T_{1}$ at temperatures above 20 K is well explained by paramagnetic thermal spin fluctuations where the fluctuation frequency of Cu $^{2 +}$ spins is higher than the NMR frequency of the order of MHz. However, a clear signature of the slowing down of the Cu $^{2 +}$ spin fluctuations was observed at low temperatures where 1/ $T_{1}$ shows a thermally-activated behavior. The magnetic field dependence of the magnitude of the spin excitation gap suggests that the magnetic behaviors of CCCO are characterized as an AFM chain at low temperatures.

arXiv comment5 pages, 4 figures, accepted for publication as a Letter in Phys. Rev. B

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Cited by in corpus (1)

Gapless spinons and a field-induced soliton gap in the hyper-honeycomb Cu oxalate framework compound [(C $_{2}$ H $_{5}$ ) $_{3}$ NH] $_{2}$ Cu $_{2}$ (C $_{2}$ O $_{4}$ ) $_{3}$