Magnetic phase diagrams and large magnetocaloric effects of the two-dimensional antiferromagnetic triangular lattice of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow><mml:mi>Gd</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:math> ions in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow><mml:mi>KBaGd</mml:mi><mml:mo>(</mml:mo><mml:msub><mml:mi>BO</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:mo>)</mml:mo></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>
Zhenhao Song, Nan Zhao, Han Ge, Tian-Ze Li, Jiong Yang, Le Wang, Ying Fu, Yicai Zhang, S. M. Wang, Jia‐Wei Mei, Hong S. He, Songwei Guo, Liusuo Wu, Jieming Sheng
Abstract
We report a detailed study of the magnetic properties of $\mathrm{KBaGd}{({\mathrm{BO}}_{3})}_{2}$ in which magnetic ${\mathrm{Gd}}^{3+}$ $(S=7/2)$ ions form into two-dimensional triangular layers. Magnetization, specific heat, and magnetocaloric effect (MCE) measurements were performed on $\mathrm{KBaGd}{({\mathrm{BO}}_{3})}_{2}$ single crystals. The results show that a long-range antiferromagnetic state is established below ${T}_{\mathrm{N}}=0.24$ K. In zero fields, only about half of the full entropy is released at ${T}_{\mathrm{N}}$, indicating that not all the magnetic moments are frozen below the ordering temperature, as expected from the geometrical frustration of the triangular spin lattice. Further studies under external fields were performed down to 50 mK and the magnetic phase diagrams are established with magnetic fields applied both within and perpendicular to the triangular plane. $\mathrm{KBaGd}{({\mathrm{BO}}_{3})}_{2}$ serves as an example of a two-dimensional triangular lattice with large spin values $(S=7/2)$ and can be directly compared with the isostructure $\mathrm{KBaR}{({\mathrm{BO}}_{3})}_{2}$ $(\mathrm{R}=\mathrm{Dy}\text{\ensuremath{-}}\mathrm{Yb})$ family of doublet ground states, which exhibit effective spins of $S=1/2$.