1202.2913 (Yoshihiko Okamoto et al.)

Distorted Kagome Lattice Generated by a Unique Orbital Arrangement in
the Copper Mineral KCu3As2O7(OH)3    [PDF]

Yoshihiko Okamoto, Hajime Ishikawa, Goeran J. Nilsen, Zenji Hiroi

We study polycrystalline samples of KCu3As2O7(OH)3, a new candidate spin-1/2
kagome antiferromagnet, by magnetic susceptibility and heat capacity
measurements above 2 K. The unique arrangement of the 3z2 - r2 and x2 - y2
orbitals on the Cu2+ kagome net is noted and compared to the orbital patterns
found in other kagome minerals. It is suggested that this orbital arrangement
gives rise to one antiferromagnetic and two ferromagnetic interactions on
isosceles triangles forming a highly distorted kagome lattice. KCu3As2O7(OH)3
is found to show an antiferromagnetic long-range order at T_N = 7.2 K.
Remarkably, a spin entropy is more gradually released upon cooling below T_N
compared with a conventional magnetic long-range order, which may originate
from the geometrical frustration still present in this highly distorted kagome
lattice.

View original: http://arxiv.org/abs/1202.2913