Field-induced magnetic order in DyTa${}_7$O${}_{19}$ with two-dimensional pseudospin-$\frac{1}{2}$ triangular lattice

The magnetic ground state of geometrically frustrated antiferromagnet attracts great research interests due to the possibility to realize novel quantum magnetic state such as a quantum spin liquid. Here we present a comprehensive magnetic characterization of DyTa${}_7$O${}_{19}$ with ideal two-dimensional triangular lattice. DyTa${}_7$O${}_{19}$ exhibits $c$-axis single-ion magnetic anisotropy. Although long-range magnetic order is not observed down to 100 mK under zero field, by applying a small magnetic field ($\sim$0.1 T), a magnetically ordered state with net magnetization of $M_s$/3 below $T_m$=0.14 K is identified ($M_s$ denotes the saturated magnetization). We argue that this state is an up-up-down magnetic structure phase driven by the dipole-dipole interactions between Ising-like spins of Dy${}^{3+}$ in a two-dimensional triangular lattice, since its ordering temperature and temperature-field phase diagram can be well explained by the theoretical calculations based on dipolar interactions. DyTa${}_7$O${}_{19}$ could be viewed as a rare material platform that realizing pure Ising-like dipolar interaction in a geometrically frustrated lattice.