Anisotropic In-Plane Strain and Transport in Epitaxial Nd(0.2)Sr(0.8)MnO(3) Thin Films

TL;DR

This study investigates how in-plane strain affects the structure and electrical transport properties of epitaxial Nd(0.2)Sr(0.8)MnO(3) thin films, revealing anisotropic strain effects and resistivity behavior across different film thicknesses.

Contribution

It provides detailed analysis of strain-induced structural and electrical anisotropies in epitaxial Nd(0.2)Sr(0.8)MnO(3) films, highlighting the effects of tensile and compressive strains on their properties.

Findings

Crystallographic c-axes remain fully strained across all thicknesses.

Resistivity anisotropy increases exponentially with film thickness.

Tensile strain enhances Neel temperature by approximately 25 K.

Abstract

The structure, morphology, and electrical properties of epitaxial a-axis oriented thin films of Nd(0.2)Sr(0.8)MnO(3) are reported for thicknesses 10 nm <= t <= 150 nm. Films were grown with both tensile and compressive strain on various substrates. It is found that the elongated crystallographic c-axes of the films remain fully strained to the substrates for all thicknesses in both strain states. Relaxation of the a and b axes is observed for t>= 65 nm with films grown under tensile strain developing uniaxial crack arrays (running along the c axis) due to a highly anisotropic thermal expansion. For the latter films, the room-temperature in-plane electrical resistivity anisotropy, rho_b/rho_c, increases approximately exponentially with increasing film thickness to values of ~1000 in the thickest films studied. Films under tension have their Neel temperatures enhanced by ~25 K independent of thickness, consistent with an enhancement of ferromagnetic exchange along their expanded c axes.