Long-range order induced by diamagnetic dilution of jarosites, model Kagomé antiferromagnets

Members of the jarosite mineral family AFe3(OH)6(SO4)2, where A is usually a univalent cation, posses a highly frustrated Kagome lattice of antiferromagnetically coupled S = 1 5 Heisenberg moments. All the members of the family show-long range magnetic order below T N ≊ 55 K except for the hydronium salt (A  H3O) which displays a spin-glass-like transition at T f ≊ 15 K . The only clear difference between the two sets if materials is that all the salts except for hydronium salt have a strong tendency to lose iron atoms from the structure when it is synthesized. When 11% of the magnetic sites are removed or replaced with diamagnetic ions in the diluted salt (D3O)Fe3−xAlx(OD)6(SO4)2, Tf rises to 25.5 K and powder neutron diffraction reveals both short- and long-range magnetic correlations at 1.4 K.