Nanoscale origins of Non-Joulian magnetostriction in Fe-Ga alloys

Recently, a new class of single-crystalline magnets exhibiting a `giant' non-volume-conserving or non-Joulian magnetostriction was discovered [1]. Electronic-structural mechanism giving rise to this unusual phenomenon is not well understood. Here we show the results of our recent investigations of non-Joulian Fe-Ga alloys using high-resolution polarization-dependent photoelectron microscopy (XMCD-PEEM), x-ray absorption spectroscopy (XAS) and hard x-ray nanodiffraction. Strong coupling between the nanoscale modulations in the magnetic and structural properties is observed. The results are compared with the state-of-the-art first-principles theoretical calculations. Combining spectromicroscopic techniques that probe electronic, magnetic and structural degrees of freedom on the nanoscale provides a powerful experimental platform for studying such materials. [1] H. D. Chopra and M. Wuttig, Non-Joulian magnetostriction, Nature 521, 340 (2015).