A new class of inherently nanolaminated magnetic materials: Magnetic MAX phases
Ulf Wiedwald, Universität Duisburg-Essen, Duisburg, GermanyRuslan Salikhov, University of Duisburg-Essen, Duisburg, GermanyQuanzheng Tao, Linköping University, Linköping, SwedenArni S. Ingason, Linköping University, Linköping, SwedenJohanna Rosén, Linköping University, Linköping, SwedenMichael 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 . 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 (Cr0.5Mn0.5)2GaC and (Cr0.5Mn0.5)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 (Cr0.5Mn0.5)2GaC film has negligibly small magnetocrystalline anisotropy energy (MAE) and a spectroscopic splitting factor of g = 2.00 ± 0.02 . The (Cr0.5Mn0.5)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.
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