Evidence of tetragonal distortion as the origin of the ferromagnetic ground state in γ-Fe nanoparticles

V. Augustyns, K. Van Stiphout, V. Joly, T. A.L. Lima, G. Lippertz, M. Trekels, E. Menéndez, F. Kremer, U. Wahl, A. R.G. Costa, J. G. Correia, D. Banerjee, H. P. Gunnlaugsson, J. Von Bardeleben, I. Vickridge, M. J. Van Bael, J. Hadermann, J. P. Araújo, K. Temst, A. VantommeL. M.C. Pereira

    Research output: Contribution to journalArticlepeer-review

    2 Citations (Scopus)

    Abstract

    γ-Fe and related alloys are model systems of the coupling between structure and magnetism in solids. Since different electronic states (with different volumes and magnetic ordering states) are closely spaced in energy, small perturbations can alter which one is the actual ground state. Here, we demonstrate that the ferromagnetic state of γ-Fe nanoparticles is associated with a tetragonal distortion of the fcc structure. Combining a wide range of complementary experimental techniques, including low-temperature Mössbauer spectroscopy, advanced transmission electron microscopy, and synchrotron radiation techniques, we unambiguously identify the tetragonally distorted ferromagnetic ground state, with lattice parameters a=3.76(2)Å and c=3.50(2)Å, and a magnetic moment of 2.45(5) μB per Fe atom. Our findings indicate that the ferromagnetic order in nanostructured γ-Fe is generally associated with a tetragonal distortion. This observation motivates a theoretical reassessment of the electronic structure of γ-Fe taking tetragonal distortion into account.

    Original languageEnglish
    Article number174410
    JournalPhysical Review B
    Volume96
    Issue number17
    DOIs
    Publication statusPublished - 7 Nov 2017

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