In the pyrochlore antiferromagnets, the magnetic ions are situated at the vertices of a framework of cornersharing 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 CsNiCrF 6 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 transition͒, the order does not extend further

more »

... han 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. ͓S0163-1829͑97͒02637-4͔