133Cs-NMR study on aligned powder of competing spin chain compound Cs2Cu2Mo3O12

TL;DR

This study investigates the hyperfine coupling in Cs2Cu2Mo3O12 using 133Cs-NMR to understand spin fluctuation anisotropy in a frustrated spin chain compound expected to exhibit nematic TLL behavior.

Contribution

It provides the first detailed measurement of the anisotropic hyperfine coupling in Cs2Cu2Mo3O12, crucial for interpreting NMR relaxation data related to spin fluctuations.

Findings

Hyperfine coupling anisotropy A_an=+770 Oe/μ_B identified.

Transverse spin fluctuations are significantly suppressed in the nematic TLL state.

Results support theoretical predictions of anisotropic spin dynamics.

Abstract

S = 1/2 competing spin chain compound Cs2Cu2Mo3O12 has two dominant exchange interactions of the nearest neighbouring ferromagnetic J1= 93 K and the second nearest neighbouring antiferromagnetic J2= +33 K, and is expected to show the nematic Tomonaga-Luttinger liquid (TLL) state under high magnetic field region. The recent theoretical study by Sato et al. has shown that in the nematic TLL state, the spin fluctuations are expected to be highly anisotropic, that is, its transverse component is suppressed. Our previous NMR study on the present system showed that the dominant contribution to nuclear spin relaxation comes from the longitudinal component. In order to conclude that the transverse component of spin fluctuations is suppressed, the knowledge of hyperfine coupling is indispensable. This article is solely devoted to investigate the hyperfine coupling of 133Cs-NMR site to prove that the anisotropic part of hyperfine coupling, which connects the nuclear spin relaxation with the transverse spin fluctuations is considerably large to be A_an=+770 Oe/mu_B.