Structural Distortions At Polar Manganite Interfaces

TL;DR

This study investigates how structural distortions and ionic intermixing at polar manganite interfaces influence electronic and magnetic properties, revealing that both phenomena coexist and are crucial for interface behavior.

Contribution

It provides direct experimental evidence of polar distortions and ionic intermixing at oxide interfaces, highlighting their combined role in interface compensation mechanisms.

Findings

Lattice expands and rumples along the growth direction at interfaces.

Intermixing of La and Sr occurs over a few unit cells.

Polar distortions and ionic intermixing coexist at the interface.

Abstract

Electronic, lattice, and spin interactions at the interfaces between crystalline complex transition metal oxides can give rise to a wide range of functional electronic and magnetic phenomena not found in bulk. At hetero-interfaces, these interactions may be enhanced by combining oxides where the polarity changes at the interface. The physical structure between non-polar SrTiO$_3$ and polar La$_{1-x}$Sr$_x$MnO$_3$(x=0.2) is investigated using high resolution synchrotron x-ray diffraction to directly determine the role of structure in compensating the polar discontinuity. At both the oxide-oxide interface and vacuum-oxide interfaces, the lattice is found to expand and rumple along the growth direction. The SrTiO$_3$/La$_{1-x}$Sr$_x$MnO$_3$ interface also exhibits intermixing of La and Sr over a few unit cells. The results, hence, demonstrate that polar distortions and ionic intermixing coexist and both pathways play a significant role at interfaces with polar discontinuities.