Structure Characterization of Colossal Magnetoresistive Oxides

Abstract Magnetoresistance describes a phenomenon in which the electrical resistance of the material depends strongly on an externally applied magnetic field. Colossal magnetoresistance (CMR) was observed in a new class of oxides, (La,A)MnO3 (A = Ca, Sr, or Ba), and the Magnetoresistance ratio of ΔR/R(H)> -100,000% has been reported in epitaxially grown La0.67Ca0.33MnO3 films. The new types of intrinsic magnetoresistive oxides offer exciting possibilities for improved magnetic sensors, magnetoresistive read heads, and magnetoresistive random access memory (MRAM). The CMR magnetic oxides have a perovskite-type crystal structure with ferromagnetic ordering in the a-b planes and antiferromagnetic ordering along the c-axis (Figure 1). The ferromagnetically ordered Mn-O layers of the a-b planes are isolated by a non-magnetic La(A)-O monolayer. This spin-coupling structure is intrinsic. La1-xAxMn03 compounds having the extreme values x = 0, 1 are neither ferromagnetic nor good electrical conductors; they are semiconductors. Only compounds with intermediate values of x are ferromagnetic,