Orthorhombic to tetragonal transition of SrRuO3 layers in Pr0.7Ca0.3MnO3/SrRuO3 superlattices

TL;DR

This study investigates how the crystalline symmetry of SrRuO3 layers in Pr0.7Ca0.3MnO3/SrRuO3 superlattices changes from orthorhombic to tetragonal as the layer thickness varies, revealing structure-property relationships.

Contribution

It demonstrates the thickness-dependent structural transition of SrRuO3 in superlattices, combining advanced microscopy and magnetoresistance measurements to elucidate the mechanisms involved.

Findings

Orthorhombic SrRuO3 at 1.5 nm Pr0.7Ca0.3MnO3 layer thickness.

Tetragonal SrRuO3 at 4.0 nm Pr0.7Ca0.3MnO3 layer thickness.

Structural transition influences magnetic and electronic properties.

Abstract

High-quality Pr0.7Ca0.3MnO3/SrRuO3 superlattices with ultrathin layers were fabricated by pulsed laser deposition on SrTiO3 substrates. The superlattices were studied by atomically resolved scanning transmission electron microscopy, high-resolution transmission electron microscopy, resistivity and magnetoresistance measurements. The superlattices grew coherently without growth defects. Viewed along the growth direction, SrRuO3 and Pr0.7Ca0.3MnO3 layers were terminated by RuO2 and MnO2, respectively, which imposes a unique structure to their interfaces. Superlattices with a constant thickness of the SrRuO3 layers, but varying thickness of the Pr0.7Ca0.3MnO3 layers showed a change of crystalline symmetry of the SrRuO3 layers. At a low Pr0.7Ca0.3MnO3 layer thickness of 1.5 nm transmission electron microscopy proved the SrRuO3 layers to be orthorhombic, whereas these were non-orthorhombic for a Pr0.7Ca0.3MnO3 layer thickness of 4.0 nm. Angular magnetoresistance measurements showed orthorhombic (with small monoclinic distortion) symmetry in the first case and tetragonal symmetry of the SrRuO3 layers in the second case. Mechanisms driving this orthorhombic to tetragonal transition are briefly discussed.