Atomically engineered cobaltite layers for robust ferromagnetism

TL;DR

This paper demonstrates how atomically precise synthesis of cobaltite layers within tilted octahedral matrices induces electronic and magnetic changes, leading to robust ferromagnetism in ultrathin cobaltites through epitaxial geometric engineering.

Contribution

It introduces a novel method of atomically engineering cobaltite heterostructures to control their magnetic properties via octahedral tilting and strain effects.

Findings

Octahedral tilting propagates into cobaltite layers, inducing electronic reconstruction.

Cobalt ions transition to a higher spin state, enhancing ferromagnetism.

The approach enables fine-tuning lattice and spin degrees of freedom in quantum heterostructures.

Abstract

Emergent phenomena at heterointerfaces are directly associated with the bonding geometry of adjacent layers. Effective control of accessible parameters, such as the bond length and bonding angles, offers an elegant method to tailor competing energies of the electronic and magnetic ground states. In this study, we construct unit thick syntactic layers of cobaltites within a strongly tilted octahedral matrix via atomically precise synthesis. The octahedral tilt patterns of adjacent layers propagate into cobaltites, leading to a continuation of octahedral tilting while maintaining significant misfit tensile strain. These effects induce severe rumpling within an atomic plane of neighboring layers triggers the electronic reconstruction between the splitting orbitals. First-principles calculations reveal that the cobalt ions transits to a higher spin state level upon octahedral tilting, resulting in robust ferromagnetism in ultrathin cobaltites. This work demonstrates a design methodology for fine-tuning the lattice and spin degrees of freedom in correlated quantum heterostructures by exploiting epitaxial geometric engineering.