Short-range magnetic order in the frustrated pyrochlore antiferromagnet CsNiCrF₆

In the pyrochlore antiferromagnets, the magnetic ions are situated at the vertices of a framework of corner-sharing tetrahedra. The result is intense geometrical frustration of the magnetic interactions. We present the results of a single-crystal neutron-diffraction study of the pyrochlore CsNiCrF₆ to investigate the development of magnetic order at low temperatures. We find that even at a temperature of 2 K (which is below the apparent spin-glass transition), the order does not extend further than two nearest neighbors, in spite of the strong antiferromagnetic interactions between spins. We also present the results of Monte Carlo calculations of the magnetic scattering utilizing a simple model Hamiltonian, and find good qualitative agreement with the experimental data.