isation 2

Contributed talk

A new class of inherently nanolaminated magnetic materials: Magnetic MAX phases

Ulf Wiedwald, Universität Duisburg-Essen, Duisburg, Germany
Ruslan Salikhov, University of Duisburg-Essen, Duisburg, Germany
Quanzheng Tao, Linköping University, Linköping, Sweden
Arni S. Ingason, Linköping University, Linköping, Sweden
Johanna Rosén, Linköping University, Linköping, Sweden
Michael Farle, University of Duisburg-Essen, Duisburg, Germany

MAX phases are inherently nanolaminated materials which are composed of an early transition metal M, an A-group element A, and either C or N, denoted X. These compounds are electrically and thermally conductive, lightweight, stiff, resistive against oxidation and can show self-healing properties [1-2]. The crystal structure of MAX phases is hexagonal with repeated M-X-M (quasi 2D) atomic layers stacking in the c-direction with an A-element spacer. Significant interest to MAX phase systems is due to the recently discovered possibility of delamination of layered MAX phase structures. This leads to 2D graphene-like MX materials with strong chemical bonds [3]. These systems, so-called MXenes, show exceptional properties important for catalysis and energy storage applications [3-4].

In 2013, the new class of magnetic MAX phases were discovered which contain Cr and Mn or a mixture of them as the M element. The magnetic properties of new (Cr_0.5Mn_0.5)₂GaC and (Cr_0.5Mn_0.5)₂GeC epitaxial films have been studied by ferromagnetic resonance, SQUID magnetometry, and X-ray magnetic circular dichroism. Both systems show ferromagnetic properties with the Curie temperature above 200 K. The (Cr_0.5Mn_0.5)₂GaC film has negligibly small magnetocrystalline anisotropy energy (MAE) and a spectroscopic splitting factor of g = 2.00 ± 0.02 [5]. The (Cr_0.5Mn_0.5)₂GeC film, however, shows a high MAE density of about 0.1 MJ/m³ at T = 100 K with the magnetic easy axis parallel to the c-axis (perpendicular to the film plane). These results show that the MAE in magnetic MAX phases can be significantly changed by the choice of the A element.

References
[1] M. W. Barsoum, Prog. Solid State Chem. 28, 201, (2000).
[2] A-S. Farle et al., J. Europ. Ceram. Soc. 35, 37-45 (2015).
[3] O. Mashtalir et al., Nature Comm. 4, 1716 (2013).
[4] M. Ghidiu et al., Nature Letter. 516, 78-81 (2014).
[5] R. Salikhov et al., Mater. Res. Lett. 3, 156 (2015).

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