Thickness Dependent Magnetotransport in Ultra-Thin Manganite Films

To understand the near-interface magnetism in manganites, uniform, ultrathin films of La_0.67Sr_0.33MnO₃ were grown epitaxially on single crystal (001) LaAlO₃ and (110) NdGaO₃ substrates. The temperature and magnetic field dependent film resistance is used to probe the film's structural and magnetic properties. A surface and/or interface related dead-layer is inferred from the thickness dependent resistance and magnetoresistance. The total thickness of the dead layer is estimated to be _~ 30 Å for films on NdGaO₃ and _~ 50 Å for films on LaAlO₃.