Hamburg 2001 – scientific programme

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AM: Magnetismus

AM 3: Magnetowiderstand I

AM 3.13: Talk

Monday, March 26, 2001, 17:30–17:45, S 5.2

Magnetotransport in La_0.7Sr_0.3MnO₃/SrTiO₃ multilayers — •Kathrin Dörr¹, Karl-Hartmut Müller¹, Mungila Sahana¹, Theresia Walter¹, Konstantin Nenkov¹, Ludwig Schultz¹, and Karin Brand² — ¹IFW Dresden, Postfach 270116, 01171 Dresden — ²TU Dresden, Institute of Applied Physics, 01062 Dresden

La_0.7Sr_0.3MnO₃ (LSMO) is a half metal that shows the colossal magnetoresistance (CMR) near the ferromagnetic Curie temperature of T_C = 370 K and metallic conductivity below. However, ultrathin (< 3 nm) films of LSMO are semiconductors with reduced magnetic order. Epitaxial strain and surface effects tend to suppress the ferromagnetic double exchange. We have studied the behavior of coherently grown LSMO / STO multilayers with ultrathin manganite layers prepared by pulsed laser deposition. HRTEM images of cross sections of the samples indicate coherent growth, fairly smooth interfaces, and a thickness-dependent undulation of layers. Magnetic measurements show a decrease of T_C with d, from 354 K for d = 10 nm to 165 K for 1.9 nm, associated with a pronounced reduction of the spontaneous magnetization. Results of in-plane magnetotransport indicate the existence of discrete ferromagnetic regions and a percolative nature of transport in the ultrathin LSMO films. In this regime, strongly non-linear transport has been observed and will be discussed.