Enhancement of intrinsic magnetoresistance in Zn doped La0.9Sr0.1MnO3 epitaxial films

Highlights: • Insight into Zn doping effects on the structural, transport and magnetic properties of LSMZO epitaxial films. • The weakening of double exchange interaction is mainly due to the substitution of Mn³⁺ by Zn²⁺. • Zn doping induces an enhancement in the intrinsic MR due to the enhanced magnetic disorder. • A fairly large MR of 26.4% under a low field of 0.3 T at 210 K is observed. -- Abstract: Mn-site doping is an effective avenue to tune the physical properties of manganites, but the underlying mechanism has rarely been explored in the epitaxial film systems doped with closed shell metal ions. Here, high-quality epitaxial La_0.9Sr_0.1Mn_1-yZn_yO₃ (LSMZO) thin films have been successfully prepared by magnetron sputtering on LaAlO₃ substrate, and the effect of Zn doping on the structural, transport and magnetic properties of the LSMZO films was investigated systematically. As Zn content increases, Curie temperature (T_C), saturation magnetization (M_S) and metal-insulator transition temperature (T_MI) are reduced, and the room-temperature resistivity is raised. Analysis on Mn³⁺/Mn⁴⁺ ratio shows the substitution of Mn³⁺ ion by Zn²⁺ ion reduces Mn³⁺/Mn⁴⁺ ratio deviating from the optimal value and thus weakening double exchange interaction. Besides that, the electron-lattice coupling stemming from the lattice distortion and Jahn-Teller (JT) effect also has a significant impact. Most significantly, Zn doping induces an enhancement in the intrinsic magnetoresistance (MR) due to the enhanced magnetic disorder, and a fairly large MR of 26.4% is obtained under a low field of 0.3 T at 210 K in the LSMZO (y = 0.20) film. Our study reveals that Zn doping at Mn site can regulate intrinsic physical properties of manganite films by modifying double exchange and electron-lattice interaction.