Epitaxial strain engineering of a high-entropy oxide

Finding new materials and new ways to tune material’s properties are essential to fulfil the

demand of the constantly evolving modern technology. High entropy oxides (HEOs) are a class

of materials, containing equimolar portions of five or more transition metal and/or rare-earth

element. HEOs are being explored in recent years to achieve tunable properties in unexplored

parts of the complex phase diagram. However, epitaxial stabilization of such multi-element

system is challenging, and it is unknown how epitaxial strain will affect the electronic and

magnetic behaviour of HEO. We have been able to grow a prototype-HEO

(LaPrNdSmEu)0.2NiO3 in layer-by-layer mode using pulsed laser deposition. Detailed

characterization using x-ray-based methods confirm excellent structural quality of these films.

We have observed that (LaPrNdSmEu)0.2NiO3 film grown under tensile strain exhibit a metalinsulator

transition (MIT). We have found that this transition can be completely suppressed by

compressive strain. Surprisingly, HEO film where the strain is almost negligible, does not

exhibit any MIT. This work firmly demonstrates the symmetry and strain effect of the

substrates on the electronic properties of a high-entropy oxide thin film.