Tuning of the metal-insulator transition in Nd-doped bilayer nickelate La₃Ni₂O₇ thin films

Recent studies have successfully demonstrated high-Tc superconductivity in bilayer nickelate La₃Ni₂O₇. However, research on modulating the structural and transport characteristics of La₃Ni₂O₇ films by applying "chemical" compressive pressure through cation substitution is still limited. Here, we address this issue in the La_3-xNd_xNi₂O₇ (x=0,1.0,1.5,2.0,2.5) thin film samples. It was found that using Nd³⁺with a smaller radius instead of La³⁺can reduce the c-axis lattice constant and shift the metal-insulator transition temperature (T_MIT). To probe the origin of metal-insulator transition (MIT) at cryogenic temperatures, experimental measurements of magnetoresistance were conducted, and theoretical analysis was carried out using Kondo model, Hikami-Larkin-Nagaoka equation, and other methods. The results indicate that as Nd doping rises, the contributions of Kondo effect and two-dimensional weak localization (WL) first decrease and then increase. The total contribution of WL and Kondo effect in the mid-doped La_1.5Nd_1.5Ni₂O₇ sample was the smallest, which to some extent explains the changes in T_MIT. Kondo effect dominates in other La_3-xNd_xNi₂O₇ (x=0,1.0,2.0,2.5) samples. This work demonstrates that cation doping has a significant impact on bilayer nickelates, providing experimental evidence for understanding the physical mechanism of metal-insulator transition in bilayer nickelates.