Spin Frustration in Some Magnetic Compounds

In the paper the results of the powder neutron diffraction measurements of RAuIn (R = Ce, Tb, Dy, and Er) and ZnFe_2O_4 compounds at low temperatures are presented. For the RAuIn compounds, which crystallize in the hexagonal ZrNiAl-type structure, the rare-earth moments lie in the ab-plane and form a typical triangle non-collinear structure. ZnFe_2O_4 has the normal spinel structure in which the Fe^{3+} ions occupy the B sites, forming the corner-shared tetrahedra of the Fe spins. At low temperatures experimental data indicate the coexistence of the long-range and the short-range magnetic order. The obtained results suggest that the important factor which influences the magnetic ordering in these compounds is geometrical frustration of magnetic moments.