paper

Helical Ordering of Spin Trimers in a Distorted Kagome Lattice of GdRuAl Studied by Resonant X-ray Diffraction

arXiv:1901.04231 · doi:10.7566/JPSJ.88.023704

Abstract

Successive magnetic phase transitions at =17.5 K and =18.5 K in GdRuAl, with a distorted kagome lattice of Gd ions, is studied using resonant X-ray diffraction with polarization analysis. It has been suggested that in this compound the spins on the nearest-neighbor Gd-triangle form a ferromagnetic trimer and the Gd lattice can be effectively considered as an antiferromagnetic triangular lattice of spin trimers [S. Nakamura et al., Phys. Rev. B 98, 054410 (2018)]. We show that the magnetic order in this system is described by an incommensurate wave vector ~(0.27, 0, 0), which varies slightly with temperature. In the low temperature phase below , the experimental results are well explained by considering that the spin trimers form a helical order with both the -axis and -plane components. In the intermediate phase above , the -axis component vanishes, resulting in a sinusoical structure within the -plane. The sinusoidal-helical transition at can be regarded as an ordering of chiral degree of freedom, which is degenerate in the intermediate phase.

5 pages, 6 figures, 2 supplemental figures, accepted for publication in J. Phys. Soc. Jpn

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