Dilution induced magnetic localization in Rb(Co1−xNix)2Se2 single crystals

We report experimental studies on a series of Rb(Co1−xNix)2Se2 (0.02 ≤x≤ 0.9) powder and single crystal samples using x-ray diffraction, neutron diffraction, magnetic susceptibility, and electronic transport measurements. All compositions are metallic and adopt the body-centered tetragonal structure with I4/mmm space group. Anisotropic magnetic susceptibilities measured on single crystal samples suggest that Rb(Co1−xNix)2Se2 undergo an evolution from ferromagnetism to antiferromagnetism, and finally to paramagnetism with increasing Ni concentration. Neutron diffraction measurements on the samples with x = 0.1, 0.4, and 0.6 reveal an A-type antiferromagnetic order with moments lying in the ab plane. The moment size changes from 0.69 (x=0.1) to 2.80μB (x=0.6) per Co ions. Our results demonstrate that dilution of the magnetic Co ions by substitution of nonmagnetic Ni ions induces magnetic localization and evolution from itinerant to localized magnetism in Rb(Co1−xNix)2Se2. •Dilution of Co ions in Rb(Co1−xNix)2Se2 enhances the moment size of the Co ions.•Replacing Co with Ni tunes the ground state progressively.•The superconductivity in RbNi2Se2 is suppressed by 10% Co-doping.•Rb(Co1−xNix)2Se2 is a suitable platform to investigate two-dimensional magnetism..