arXiv subjects

Songnan Sun

Publications and source records attributed to Songnan Sun.

3 recordsLinked to original sources

arXiv2025

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.

cond-mat.str-el↗

arXiv2024

Structural and magnetic characterization of CeTa$_7$O$_{19}$ and YbTa$_7$O$_{19}$ with two-dimensional pseudospin-1/2 triangular lattice

Triangular lattice antiferromagnets are prototypes for frustrated magnetism and may potentially realize novel quantum magnetic states such as a quantum spin liquid ground state. A recent work suggests NdTa$_7$O$_{19}$ with rare-earth triangular lattice is a quantum spin liquid candidate and highlights the large family of rare-earth heptatantalates as a framework for quantum magnetism investigation. In this paper, we report the structural and magnetic characterization of CeTa$_7$O$_{19}$ and YbTa$_7$O$_{19}$. Both compounds are isostructural to NdTa$_7$O$_{19}$ with no detectable structural disorder. For CeTa$_7$O$_{19}$, the crystal field energy levels and parameters are determined by inelastic neutron scattering measurements. Based on the crystal field result, the magnetic susceptibility data could be well fitted and explained, which reveals that CeTa$_7$O$_{19}$ is a highly anisotropic Ising triangular-lattice antiferromagnet ($g_z$/$g_{xy}$$\sim$3) with very weak exchange interaction (J$\sim$0.22~K). For YbTa$_7$O$_{19}$, millimeter sized single crystals could be grown. The anisotropic magnetization and electron spin resonance data show that YbTa$_7$O$_{19}$ has a contrasting in-plane magnetic anisotropy with $g_z$/$g_{xy}$$\sim$0.67 similar as that of YbMgGaO$_4$. The above results indicate that CeTa$_7$O$_{19}$ and YbTa$_7$O$_{19}$ with pseudospin-1/2 ground states might either be quantum spin liquid candidate materials or find applications in adiabatic demagnetization refrigeration due to the weak exchange interaction.

cond-mat.str-el↗

arXiv2024

Magnetic properties of van der Waals layered single crystals DyOBr and SmOCl

Two-dimensional van der Waals single crystals DyOBr and SmOCl have been grown by flux method and their anisotropic magnetic properties are reported. DyOBr orders antiferromagnetically at T$_{N}$=9.5 K with magnetic moments lying along $a$-axis, similar as DyOCl. Its magnetic susceptibility shows an anomaly at T$^{*}$=30 K possibly due to the crystal field effect. Furthermore a 1/3 magnetization plateau is clearly observed under H$\parallel$a and H$\parallel$[110], which might be a field-induced spin-flop phase or some exotic quantum magnetic state. On the other hand, isostructural SmOCl undergoes an antiferromagnetic transition at T$_{N}$=7.1 K and exhibits a contrasting Ising-like perpendicular $c$-axis magnetic anisotropy, which could be well explained by our crystal field calculations. Both DyOBr and SmOCl are insulators with band gap of $\sim$5 eV, our results suggest they are promising in building van der Waals heterostructures and applications in multifunctional devices.

cond-mat.mtrl-sci↗