Silver addition in polycrystalline La0.7Ca0.3MnO3: Large magnetoresistance and anisotropic magnetoresistance for manganite sensors

Highlights: • The polycrystalline La_0.7Ca_0.3MnO₃:Ag_0.2 obtained vast MR and AMR (84.1% and 32%) near room temperature. • The electron–scattering and small–polaron hopping models have been used to successfully fit the resistivity data, which support the spin–orbit coupling effect under different magnetic fields that enhance the AMR. • The polycrystalline La_0.7Ca_0.3MnO₃:Ag_x was successfully fabricated by sol–gel and solid−phase addition methods. -- Abstract: Perovskite manganite La_1−yCa_yMnO₃ has giant and tunable magnetoresistance (MR) and anisotropic magnetoresistance (AMR), still the following two challenges are of great concern: (i) large magnetic field is required for achieving excellent electromagnetic performance; and (ii) metal–insulator (M–I) transition temperature (T_MI) significantly different from room temperature; both these factors limit its practical applications. In this study, polycrystalline La_0.7Ca_0.3MnO₃:Ag_x composites were fabricated by sol–gel and solid–phase addition methods, and large MR and AMR (84.1% and 32%, respectively) were obtained at near room temperature in 1 T magnetic field when x = 0.2. Evidently, it was found that the grain boundary scattering effects were weakened due to Ag−addition, which resulted in an enhancement of MR. The tremendously high AMR value was attributed to the anisotropic spin–orbit coupling (SOC) effect. The electron–scattering and small–polaron hopping models were used to successfully fit the resistivity data, which support the SOC effect under different magnetic fields that enhance the AMR. These results support further development of the perovskite manganese oxide with potential applications in manganite devices.