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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 SrCo$_2$V$_2$O$_8$ under a longitudinal magnetic field by susceptibility and $^{51}$V NMR measurements. The bulk susceptibility $χ$ shows an onset of long-range Ising-antiferromagnetic (AFM) order and the suppression of the order by field with the Néel temperature dropped from 5.1~K to 2~K when field increases from 0.1~T 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, $χ$ 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$\bar1$0] directions. The $1/T_1$ data at higher temperature show a power-law behavior $1/T_1{\sim}T^α$, which is consistent with the Tomonaga-Luttinger-liquid behavior. With increasing the field, the power-law exponent $α$ changes from negative to positive, which clearly shows an inversion of the Luttinger exponent $η$, where the dominant low-energy spin fluctuations switch from the longitudinal type to the transverse type at a high field of 7~T.