Magnetic interactions in the tripod kagome antiferromagnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Mg</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Gd</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi>Sb</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>14</mml:mn></mml:msub></mml:mrow></mml:math> probed by static magnetometry and high-field ESR spectroscopy
C. Wellm, J. Zeisner, A. Alfonsov, Mihai Sturza, Gaël Bastien, S. Gaß, S. Wurmehl, A. U. B. Wolter, B. Büchner, V. Kataev
Abstract
We report an experimental study of the static magnetization $M(H,T)$ and high-field electron spin resonance (ESR) of polycrystalline ${\text{Mg}}_{2}{\text{Gd}}_{3}{\text{Sb}}_{3}{\text{O}}_{14}$, a representative member of the newly discovered class of the so-called tripod kagome antiferromagnets where the isotropic ${\mathrm{Gd}}^{3+}$ spins $(S=7/2)$ form a two-dimensional kagome spin-frustrated lattice. It follows from the analysis of the low-$T\phantom{\rule{4pt}{0ex}}M(H)$ curves that the ${\mathrm{Gd}}^{3+}$ spins are coupled by a small isotropic antiferromagnetic (AFM) exchange interaction, $|J|\ensuremath{\approx}0.3$ K. The $M(H,T)$ dependences measured down to 0.5 K evidence a long-range AFM order at ${T}_{N}=1.7\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ and its rapid suppression at higher fields, $\ensuremath{\ge}4$ T. ESR spectra measured in fields up to 15 T are analyzed considering possible effects of demagnetizing fields, single-ion anisotropy, and spin-spin correlations. While the demagnetization effects due to a large sample magnetization in high fields and its shape anisotropy become relevant at low temperatures, the broadening of the ESR line commencing already at $T\ensuremath{\lesssim}30\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ may indicate the onset of the spin-spin correlations far above the ordering temperature due to the geometrical spin frustration in this compound.