Magnetic ordering in metallic TlCo2−xNixS2 (0 ⪕ x ⪕ 2.0) with the ThCr2Si2 structure

Abstract Solid solutions of TlCo2−xNixS2 (0 ⪕ x ⪕ 2.0) with the ThCr2Si2-type structure were prepared by high temperature solid state reaction. All of the samples are highly metallic (δ ∼ 10-4-10-5 Ω-cm). TlCo2S2 orders ferromagnetically at ∼ 152 K, and TlNi2S2 is Pauli paramagnetic. Substitution of Co by Ni in TlCo2−xNixS2 (0.05 ⪕ x ⪕ 1.25) results in antiferromagnetic behavior. The magnetic moments localized on the Co ions in TlCo2S2 have been found to be oriented parallel with the a crystallographic direction as determined by magnetic measurements on an oriented single crystal. The magnetic structure of TlCo2−xNixS2 and the possible role of Ni ions in the solid solutions is discussed.