A novel magnetoresistance induced by charge ordering in ferromagnetic/charge-ordered/ferromagnetic trilayers

Microstructure, magnetoresistance (MR) and magnetic properties of Pr_0.7Sr_0.3MnO₃/La_0.5Ca_0.5MnO₃/Pr_0.7Sr_0.3MnO₃ trilayers, which are shown to be tunable with different La_0.5Ca_0.5MnO₃ spacer thickness, are investigated. The trilayer with 6 nm thick La_0.5Ca_0.5MnO₃ spacer show $\text{MR}\sim 37\%$ at 195 K in 1 T and $\text{MR}\sim 80\%$ at 220 K in 9 T, which is realized through the double-exchange mechanism. In contrast, trilayers with the thicker La_0.5Ca_0.5MnO₃ spacer show enhanced MR at a wide low-temperature range. The obtained $\text{MR}\sim 52\%$ at 50 K in 1 T in the trilayer with 18 nm thick La_0.5Ca_0.5MnO₃ spacer is superior to that of other magnetic nanoscales. We surmise that this MR originates in the ferromagnetic/antiferromagnetic competition accompanied with the formation of a charge-ordered antiferromagnetic state and the collapse of the charge-ordered state at the applied magnetic field, rather than in the double-exchange mechanism. Large and tunable MR can be realized by controlling the strain state (the thickness of the La_0.5Ca_0.5MnO₃ spacer), which can be applied in the used devices. (letter)