Spatially Inhomogeneous Metal-Insulator Transition in Doped Manganites.
Scanning tunneling spectroscopy was used to investigate single crystals and thin films of La(1-x)Ca(x)MnO(3) (with x of about 0.3), which exhibit colossal magnetoresistance. The different spectroscopic signatures of the insulating (paramagnetic) and metallic (ferromagnetic) phases enable their spatial extent to be imaged down to a lateral scale of the order of 10 nanometers. Above the bulk transition temperature T(c), the images show mostly insulating behavior. Below T(c), a phase separation is observed where inhomogeneous structures of metallic and more insulating areas coexist and are strongly field dependent in their size and structure. Insulating areas are found to persist far below T(c). These results suggest that the transition and the associated magnetoresistance behavior should be viewed as a percolation of metallic ferromagnetic domains.
Fäth
M
Kamerlingh Onnes Laboratory, Leiden University, Post Office Box 9504, 2300 RA Leiden, Netherlands. Van der Waals-Zeeman Laboratory, University of Amsterdam, Valckenierstraat 67, 1018 XE Amsterdam, Netherlands. Joint Research Center for Atom Technology, 1-1-4 Higashi, Tsukuba, Ibaraki 305-0046, Japan.
Freisem
S
Menovsky
AA
Tomioka
Y
Aarts
J
Mydosh
JA