Distinct magnetic ground states in Shastry-Sutherland lattice materials: <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi mathvariant="normal">P</mml:mi><mml:msub><mml:mi mathvariant="normal">r</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">B</mml:mi><mml:msub><mml:mi mathvariant="normal">e</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi>Ge</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>7</mml:mn></mml:msub></mml:mrow></mml:math> versus <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi mathvariant="normal">N</mml:mi><mml:msub><mml:mi mathvariant="normal">d</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">B</mml:mi><mml:msub><mml:mi mathvariant="normal">e</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi>Ge</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>7</mml:mn></mml:msub></mml:mrow></mml:math>
Andi Liu, Fangyuan Song, Yaotao Cao, Han Ge, Huanpeng Bu, Jin Zhou, Yuqi Qin, Qingyuan Zeng, Jingxin Li, Langsheng Ling, Wei Tong, Jieming Sheng, Ming Yang, Liusuo Wu, Hanjie Guo, Zhaoming Tian
Abstract
The rare-earth (RE) based Shastry-Sutherland lattice (SSL) materials have attracted recent attention for exploring the exotic magnetic phases of $4f$ electrons. Here, we present a comparative study on low-temperature magnetization and specific-heat results of two tetragonal structure compounds ${RE}_{2}\mathrm{B}{\mathrm{e}}_{2}\mathrm{Ge}{\mathrm{O}}_{7}$ ($RE=\mathrm{Pr}$, Nd), where the non-Kramers $\mathrm{P}{\mathrm{r}}^{3+}$ ($J=4$) ions and Kramers $\mathrm{N}{\mathrm{d}}^{3+}$ ($J=9/2$) ions are located on the SSL geometry with ``AA''-type stacking fashion along the [001] axis. Temperature-dependent magnetic susceptibility and isothermal field-dependent magnetization $M$($B$) measurements reveal that these two compounds share a similar Ising-like magnetic anisotropy with easy magnetization along the [001] axis and additional fourfold symmetry within the $ab$ plane. For their magnetic ground states, $\mathrm{N}{\mathrm{d}}_{2}\mathrm{B}{\mathrm{e}}_{2}\mathrm{Ge}{\mathrm{O}}_{7}$ exhibits the coexistence of short-range spin correlation and long-range magnetic order with ${T}_{\mathrm{N}}=0.26$ K in zero magnetic field, while $\mathrm{P}{\mathrm{r}}_{2}\mathrm{B}{\mathrm{e}}_{2}\mathrm{Ge}{\mathrm{O}}_{7}$ does not show any signature of long-range magnetic ordering at temperatures as low as 0.08 K. The ac susceptibility and specific-heat analysis of $\mathrm{P}{\mathrm{r}}_{2}\mathrm{B}{\mathrm{e}}_{2}\mathrm{Ge}{\mathrm{O}}_{7}$ reveal a dynamic spin-freezing behavior below \ensuremath{\sim}0.22 K similar to that observed in Pr-based pyrochlore spin-ice systems.