Exchange-Driven Magnetoelastic Coupling in a Strongly Correlated Electron Material

The electronic properties of materials are the result of an intricate relationship between lattice and electronic degrees of freedom. An example of such a relationship is magnetostriction, where changing the magnetic ground state leads to changes in the lattice constant and to modifications of the electronic band structure, and vice-versa. When electronic correlations are introduced, the coupling between the degrees of freedom becomes more complex, making it challenging to discern the individual roles of each degree of freedom. This co-dependent relationship in strongly correlated electron materials results in the emergence of unconventional electronic phases, such as high-temperature superconductivity and colossal magnetoresistance. A key understanding to enable enhancement of these phases is how the coupling between electronic and lattice degrees of freedom are modified by electronic correlations.

In this talk, I will discuss the detection of changes to the electronic structure, magnetic ground state and lattice in-situ in the same experiment using scanning tunneling microscopy and spectroscopy (STM/STS). We measure these effects in the itinerant ferromagnet Sr₄Ru₃O₁₀, where electron correlations driven by proximity of Van Hove singularities to the Fermi level play an important role in determining its magnetic and electronic properties. By switching between ferromagnetic and anti-ferromagnetic alignment of the magnetization of the surface and subsurface layers in a controlled way, we study the impact of exchange interaction on the electronic structure of this material. Using STM-based magnetostriction, we detect jumps in the interlayer spacing, revealing giant exchange magnetostriction in Sr₄Ru₃O₁₀. By demonstrating a direct link between exchange interaction, electronic structure and crystal structure, our measurements provide a platform to test theoretical descriptions of strongly correlated electron materials.

This work was done in collaboration with L.C. Rhodes, W. Osmolska, H. Lane, I. Benedičič, M. Naritsuka, P. Wahl (St Andrews), R. Fittipaldi, M. Lettieri and A. Vecchione (CNR-SPIN).