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

Date

2017

Authors

Augustyns, V
van Stiphout, K
Joly, V
Lima, T A L
Lippertz, G
Trekels, M
Menéndez, E
Kremer, Felipe
Wahl, U
Costa, A R G

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Volume Title

Publisher

American Physical Society

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.

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Citation

Source

Physical Review B: Condensed Matter and Materials

Type

Journal article

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Access Statement

Open Access

License Rights

DOI

10.1103/PhysRevB.96.174410

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