Electronegative effect in layered double-perovskite La1.9Ba0.1CuSnO6 adjusted by non-magnetic Zn doping

Abstract

The La1.9Ba0.1Cu1−yZnySnO6 (0 ≤ y ≤ 0.25) (LBCZSO) ceramics were synthesized by the solid-state reaction, and the effect of non-magnetic Zn2+ ion doping on the crystal structure and electrical and magnetic properties is systematically investigated. It is found that all the samples are layered double perovskite with a space group P21/m. The resistivity ρ(T) shows a semiconductor behavior, which follows Mott's 3D variable-range hopping mode. The magnetizations M(T) and the isothermal M-H loops reveal the coexistence of ferromagnetic (FM) and antiferromagnetic (AFM) interactions in the 2D CuO2 layer. With increasing Zn doping at Cu sites, the resistivity ρ(T) increases, the FM transition temperature TC decreases, the FM/AFM interactions weaken/enhance, and the ground state of the system changes from FM to AFM one. It is suggested that cationic electronegativity plays an important role in understanding the transport and magnetic properties of the non-magnetic Zn-doped La1.9Ba0.1CuSnO6, besides the cationic radius. Since the smaller electronegativity of Cu2+ ions compared to that of Sn4+ ions, the CuO6 octahedral distortion with the in-plane compressive strain and out-plane tensile strain is induced by the lattice mismatch between CuO2 and SnO2 layers, forming C-type AF structure with the spin-canted weak FM in 2D CuO2 plane. Since the different cationic electronegativities of Zn2+ and Cu2+ ions, non-magnetic Zn doping leads to the charge transfer between Zn and Cu ions, resulting in the electronic redistribution (transformation) along the ordered Cu–O–Zn chains and non-magnetic Cu+ ions in LBCZSO, which further speeds up the decrease of TC, lead to the abnormal change in the hopping energy W and Curie temperature Θ. Besides, it is confirmed that there is a spin-glass state transition at around 26 K in the non-magnetic Zn doping La1.9Ba0.1CuSnO6 compound.