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VOLUME 60 (1994) | ISSUE 10 | PAGE 727
Nature of the giant magnetoresistance in ferromagnetic lanthanum manganites
A qualitative explanation is offered for the unusually high value (by a factor of nearly 1300) of the magnetoresistance which was recently discovered in epitaxial La-Ca-Mn-0 films. The effect is attributed to the existence of a spatially nonuniform magnetic order in the samples, which leads to a percolation metal-semiconductor transition. This interpretation is supported by results found previously by the present authors in electrical, magnetic, and NMR measurements on lanthanum manganites with similar properties. It is argued that equally high values of the magneotresistance should be observed in a wide range of compositions, in particular, in Lag 9Nao jMnj _^Mex03 (Me=Re,Cu,Co), if these materials are prepared as single crystals or epitaxial films. The magnetoresistance of these ceramics in weak fields (<1 kOe) is higher than that of La-Ca-Mn-0 films. © 1994 American Institute of Physics.