Strain control of a bandwidth-driven spin reorientation in Ca$_{3}$Ru$_{2}$O$_{7}$

TL;DR

This study demonstrates that applying uniaxial strain to Ca$_{3}$Ru$_{2}$O$_{7}$ can control a coupled structural, electronic, and magnetic phase transition by tuning the electronic bandwidth through lattice distortions.

Contribution

It provides experimental evidence that strain can drive a bandwidth-controlled spin reorientation, supported by a theoretical model of strain-induced phase transition mechanisms.

Findings

Transition driven by externally applied strain.

Strain modifies RuO$_{6}$ octahedral tilts and rotations.

Potential for controlling phase transitions via strain.

Abstract

The layered-ruthenate family of materials possess an intricate interplay of structural, electronic and magnetic degrees of freedom that yields a plethora of delicately balanced ground states. This is exemplified by Ca$_{3}$Ru$_{2}$O$_{7}$, which hosts a coupled transition in which the lattice parameters jump, the Fermi surface partially gaps and the spins undergo a $90^{\circ}$ in-plane reorientation. Here, we show how the transition is driven by a lattice strain that tunes the electronic bandwidth. We apply uniaxial stress to single crystals of Ca$_{3}$Ru$_{2}$O$_{7}$, using neutron and resonant x-ray scattering to simultaneously probe the structural and magnetic responses. These measurements demonstrate that the transition can be driven by externally induced strain, stimulating the development of a theoretical model in which an internal strain is generated self-consistently to lower the electronic energy. We understand the strain to act by modifying tilts and rotations of the RuO$_{6}$ octahedra, which directly influences the nearest-neighbour hopping. Our results offer a blueprint for uncovering the driving force behind coupled phase transitions, as well as a route to controlling them.