The Dead Layer and Critical Behavior of La23 Sr13 MnO3 Ultra Thin Film
Dead layer - the insulating behavior in ultrathin films of metallic oxides - is an intriguing property of thin TMO films. The question is, is this effect caused by dimensional confinement, or by the interface, strain, segregation, impurity, or stoichiometry.
Utilizing UHV Laser-MBE growth technique, we have systematically studied the thickness-dependence of structure/properties for La23 Sr13 MnO3 (LSMO) on SrTiO3(001) by using in-situ characterization such as LEED, XPS and STM, and ex-situ transport measurements.
With optimized growth conditions to minimize the oxygen deficiency (oxygen non-stoichiometry), we were able to focus on the other effects associated with the dead layer. In this talk, I will summarize our recent results on the dead layer of LSMO by showing that the dimensionality/structure effects play key role in determining the dead layer.
With this optimized quality of ultrathin films, new critical behaviors emerge, such as the non-monotonic structure relaxation with thickness, the enhanced magnetoresistance effect and extreme sensitivity to strain at the critical thickness at 6 unit cells. These behaviors are proposed to correlate with subtle balance of different competing effects.
Supported by the US Department of Energy.