Field-induced antiferromagnetism and Tomonaga-Luttinger liquid behavior in the quasi-one-dimensional Ising antiferromagnet SrCo2V2O8

We investigate the low-temperature properties of the Ising-like screw chain antiferromagnet ${\mathrm{SrCo}}_{2}{\mathrm{V}}_{2}{\mathrm{O}}_{8}$ under a longitudinal magnetic field by susceptibility and $^{51}\mathrm{V}$ NMR measurements. The bulk susceptibility $\ensuremath{\chi}$ shows an onset of long-range Ising-antiferromagnetic (AFM) order and the suppression of the order by field with the N\'eel temperature dropped from 5.1 to 2 K when field increases from 0.1 to 4 T. The suppression of the AFM order by the field is also observed by the NMR spectra and the spin-lattice relaxation $1/{T}_{1}$. At fields above 4 T, $\ensuremath{\chi}$ shows a low-temperature upturn, which is consistent with the onset of a transverse antiferromagnetic order as supported by the quantum Monte Carlo simulations. A line splitting in the NMR spectra is also observed at high temperatures. We show that the line split characterizes the onset of a short-range transverse antiferromagnetic order with magnetic moments orientated along the crystalline $[110]/[1\overline{1}0]$ directions. The $1/{T}_{1}$ data at higher temperature show a power-law behavior $1/{T}_{1}\ensuremath{\sim}{T}^{\ensuremath{\alpha}}$, which is consistent with the Tomonaga-Luttinger-liquid behavior. With increasing the field, the power-law exponent $\ensuremath{\alpha}$ changes from negative to positive, which clearly shows an inversion of the Luttinger exponent $\ensuremath{\eta}$ where the dominant low-energy spin fluctuations switch from the longitudinal type to the transverse type at a high field of 7 T.