X-Ray Free-Electron Laser Observation of Giant and Anisotropic Magnetostriction in β-O_{2} at 110 Tesla.

In strong magnetic fields beyond 100 T, the significant Zeeman energy competes with the lattice interactions, where a considerable magnetostriction is expected. However, the microscopic observation of the magnetostriction above 100 T has been hindered due to the short pulse duration of microseconds and the coil's destruction. Here, we report the observation of the giant and anisotropic magnetostriction of ∼1% at 110 T in the spin-controlled crystal β-O_{2} by combining the single-shot diffraction of an x-ray free-electron laser (XFEL) and the newly developed portable 100 T generator (PINK-02). The soft and anisotropic response of β-O_{2} should originate in the competing van der Waals force and exchange interaction and also the frustration of spin and lattice on the triangular network. The XFEL experiment above 100 T using PINK-02 enables microscopic investigations on materials' properties at high magnetic fields, providing insights into how spins contribute to the stability of crystal structures.