Whirling spin order in the quasicrystal approximant Au${}_{72}$Al${}_{14}$Tb${}_{14}$

Abstract

Neutron powder diffraction experiment has been performed on the quasicrystal approximant Au${}_{72}$Al${}_{14}$Tb${}_{14}$, a body-center-cubic crystal of icosahedral spin clusters. The long-range antiferromagnetic order was confirmed at the transition temperature $T_{\mathrm{N}}=10.4$ K. The magnetic structure consists of noncoplanar whirling spins on the icosahedral clusters, arranging antiferroic-manner. A simple icosahedral spin-cluster model with uniaxial anisotropy accounts well the whirling spin order as well as the in-field metamagnetic transition, indicating that the icosahedral symmetry is essential.

6 pages, 4 figures