Tuning of crystal structure and magnetic properties by exceptionally large epitaxial strains

TL;DR

This study demonstrates how large epitaxial strains in Fe70Pd30 films induce significant crystal structure distortions, enabling tuning of magnetic properties across a broad range by coherent substrate growth.

Contribution

It introduces a method to achieve and control large epitaxial strains in Fe70Pd30 films, revealing their impact on crystal structure and magnetic properties.

Findings

Epitaxial strain up to 8.3% achieved in Fe70Pd30 films.

Tetragonal distortion varies from c/abct=1.09 to 1.39.

Magnetic properties like Curie temperature and anisotropy are broadly tunable.

Abstract

Huge deformations of the crystal lattice can be achieved in materials with inherent structural instability by epitaxial straining. By coherent growth on seven different substrates the in-plane lattice constants of 50 nm thick Fe70Pd30 films are continuously varied. The maximum epitaxial strain reaches 8,3 % relative to the fcc lattice. The in-plane lattice strain results in a remarkable tetragonal distortion ranging from c/abct = 1.09 to 1.39, covering most of the Bain transformation path from fcc to bcc crystal structure. This has dramatic consequences for the magnetic key properties. Magnetometry and X-ray circular dichroism (XMCD) measurements show that Curie temperature, orbital magnetic moment, and magnetocrystalline anisotropy are tuned over broad ranges.