Effect of interlayer-induced asymmetrical stress on magnetotransport properties of epitaxial [Pr0.7Sr0.3MnO3/La0.5Ca0.5MnO3]20 superlattice

Perovskite manganite R_1-xA_xMnO₃ (R=rare earth, A=alkaline earth) has been attracting great research interesting due to its magnetoelectronic phenomena such as colossal magnetoresistance (CMR), charge-orbital ordering, and metal-insulator transitions, etc.[1,2] In manganite superlattice, interfacial effects including cation intermixing, charge transfer, exchange coupling, strain and defect formation are crucial in determining the magnetic and transport properties of superlattice. [3-5] In this work, all-manganite [Pr_0.7Sr_0.3MnO₃/La_0.5Ca_0.5MnO₃]₂₀ superlattices were epitaxially fabricated on (001)-oriented single crystal MgO substrates with 24 nm La_0.5Ca_0.5MnO₃ buffer layer by using plused laser deposition. All the as-grown superlattices are of single phase and single orientation (see Fig.1). We obtained various stress at interface by varying relative layer thickness. As the thickness of Pr_0.7Sr_0.3MnO₃ layer and La_0.5Ca_0.5MnO₃ layer is not identical, interlayer-induced asymmetrical stress will occur and result in lower metal-insulator (MI) transition temperature and larger magnetoresistance (MR) in a wider temperature range. This result indicated that [Pr_0.7Sr_0.3MnO₃/La_0.5Ca_0.5MnO₃]₂₀ has opportunities for practical application in magnetic sensor and magnetic memory material. Furthermore, the percolation model has been used to quantitatively understand the transport mechanism of superlattice (see Fig.2). Our results demonstrated that inter-layer-induced asymmetrical stress accompanied with phase separation and charge ordering could strongly influence the magnetotransport properties of superlattice.