Liusuo Wu

Crystal-field symmetry restricts the ground-state Kramers doublet of ${\mathrm{ErBr}}_{3}$ to one of two classes. We show that the compressed octahedral environment selects the class with $\ensuremath{\langle}{\ensuremath{\psi}}_{\ifmmode\pm\else\textpm\fi{}}|{J}^{\ifmmode\pm\else\textpm\fi{}}|{\ensuremath{\psi}}_{\ensuremath{\mp}}\ensuremath{\rangle}=0$, suppressing the lowest-order ${J}^{\ifmmode\pm\else\textpm\fi{}}$-mediated exchange. Thermodynamic measurements reveal two zero-field anomalies at 0.375 and 0.200 K. Under an in-plane magnetic field, the thermodynamic response separates into a phase boundary and a broader crossover line. Inelastic neutron scattering measurements at 2 K reveal no well-defined low-energy dispersive magnetic modes. These results connect the ground-state symmetry with the field-dependent thermodynamic response of ${\mathrm{ErBr}}_{3}$, providing a microscopic starting point for understanding its low-energy magnetic behavior.

We report a comprehensive study of single-crystal ${\mathrm{BaNd}}_{2}{\mathrm{PdS}}_{5}$, a Shastry-Sutherland lattice (SSL) antiferromagnet. Thermodynamic and magnetization measurements identify an AFM transition at ${T}_{N}\ensuremath{\approx}3.6\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. The ${\mathrm{Nd}}^{3+}$ local-crystal-field environment imposes a rigid, mutually orthogonal Ising anisotropy, effectively splitting the SSL into two perpendicular magnetic sublattices. This orthogonal spin texture is demonstrated by a pronounced in-plane anisotropy: the saturation magnetization and the critical fields for suppressing AFM order along [100] and [110] directions differ by a factor of about $\sqrt{2}$, in close agreement with a minimal two-sublattice model. The low-temperature phase diagram for $B\ensuremath{\parallel}[110]$ reveals a field-induced quantum critical point near 2.2 T and a sublattice-selective partially polarized ordered state, in which the field-coupled sublattice is polarized while the orthogonal sublattice remains antiferromagnetically ordered. Together, these results establish ${\mathrm{BaNd}}_{2}{\mathrm{PdS}}_{5}$ as a platform to explore how lattice and site symmetries constrain collective magnetism in frustrated insulators and to guide engineering of sublattice-selective quantum criticality.