Joint publication of several CRC/TRR 270 projects and ID12 beamline at ESRF

A multi-stage, first-order phase transition in LaFe11.8Si1.2: Interplay between the structural, magnetic, and electronic degrees of freedom


K. P. Skokov, A. Y. Karpenkov, D. Y. Karpenkov, I. A. Radulov, D. Günzing, B. Eggert, A. Rogalev, F. Wilhelm, J. Liu, Y. Shao, K. Ollefs, M. E. Gruner, H. Wende, O. Gutfleisch

Applied Physics Reviews 10(3), 031408 (2023). DOI: 10.1063/5.0133411

The discontinuous nature of the transition in materials with a first-order magnetic transition is a consequence of the coupling between the magnetic, electronic, and structural subsystems, and such transition can, in principle, cross several metastable states, where at one point, the transition takes place within the magnetic subsystem, while at another, the changes occur in the structural or electronic subsystems. To disentangle the nature of such transition and relevant hysteresis mechanism, we designed two new experimental setups, allowing simultaneous measurement of magnetization, longitudinal and transversal magnetostriction and temperature change of the sample, and conducted simultaneous measurements of the prototypical LaFe11.8Si1.2 alloy and revealed rich details of the magneto-structural, first-order transition.

We found that the transition does not complete in one but in two distinct stages, which cannot be described in the framework of commonly employed thermodynamic models. We complement these findings with experiments on the atomistic scale, i.e., x-ray absorption spectroscopy, x-ray magnetic circular dichroism, and Mössbauer spectroscopy, and then combine them with first-principles calculations to reveal the full complexity and two-stage nature of the transition. The obtained results can be extended to a large class of advanced magnetic materials with itinerant moments exhibiting comparable field- and temperature-induced transformations, for example, Mn-Fe-P-Si, and Heusler-type alloys

This publication results from a collaboration of CRC/TRR 270 projects B01, A03, B05 and B06, close cooperation with ID12 beamline at ESRF, Grenoble within the framework of BMBF project “ULMAG”.