The quantum criticality of an Ising-like screw chain antiferromagnet ${\mathrm{SrCo}}_2{\mathrm{V}}_2{\mathrm{O}}_8$, with a transverse magnetic field applied along the crystalline $a$ axis, is investigated by ultralow temperature NMR measurements. The Néel temperature is rapidly and continuously suppressed by the field, giving rise to a quantum critical point (QCP) at $H_{C_1}\approx 7.03\mathrm{T}$. Surprisingly, a second QCP at $H_{C_2}\approx 7.7\mathrm{T}$ featured with gapless excitations is resolved from both the double-peak structure of the field-dependent spin-lattice relaxation rate $1/{{}^{51}T}_1$ at low temperatures and the weakly temperature-dependent $1/{{}^{51}T}_1$ at this field. Our data, combined with numerical calculations, suggest that the induced effective staggered transverse field significantly lowers the critical fields, and leads to an exposed QCP at $H_{C_2}$, which belongs to the one-dimensional transverse-field Ising universality.

${\text{Ni}}_2{\text{V}}_2{\text{O}}_7$ has an unusual skew chain structure built by magnetic ${\text{Ni}}^{2+}$ ions along the $c$ axis. Single crystals of ${\text{Ni}}_2{\text{V}}_2{\text{O}}_7$ are successfully grown by the flux method at a slow cooling rate. Magnetic properties are investigated by means of susceptibility, magnetization, and heat-capacity measurements. Our results show that the system exhibits multiple magnetic orderings at low temperature and that a metamagnetic transition occurs at the applied field along the $a$ axis.

New tellurate compounds Na₄MTeO₆ (M = Co and Ni) 1D are obtained by a high-temperature solid-state reaction, showing a unique spin-chain structure.

An enhanced MCE is observed in Gd₂Cu(SO₄)₂(OH)₄, which may be a magnetic refrigerant candidate for low-temperature applications.