Huge magnetoresistance and ultrasharp metamagnetic transition in polycrystalline Sm 0.5 Ca 0.25 Sr 0.25 MnO 3

Large magnetoresistive materials are of immense interest for a number of spintronic applications, such as the development of high-density magnetic memory devices, magnetic sensors, and magnetic switches. Colossal magnetoresistance, in which the resistivity changes by several orders of magnitude (~ 10 4 %) in an external magnetic field, occurs mainly in phase-separated oxide materials, namely, manganites, owing to the phase competition between the ferromagnetic metallic and antiferromagnetic insulating regions. Can the magnetoresistance be further enhanced by tuning the volume fraction of the two phases? In this work, we report a huge colossal magnetoresistance along with an ultrasharp metamagnetic transition in a half-doped Sm 0.5 Ca 0.25 Sr 0.25 MnO 3 manganite compound by suitably tuning the volume fraction of the competing phases. The obtained magnetoresistance value at 10 K is as large as ~ 10 13 % in a 30 kOe external magnetic field and ~ 10 15 % in a 90 kOe external magnetic field and is several orders of magnitude higher than any other observed magnetoresistance value reported thus far. Using model Hamiltonian calculations, we have shown that the inhomogeneous disorder, deduced from tunneling electron microscopy, suppresses the CE-type phase and seeds the ferromagnetic metal in an external magnetic field.