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Inhomogeneous magnetism in decagonal Al$_{69.8}$Pd$_{12.1}$Mn$_{18.1}$

D. Rau·J. L. Gavilano·Sh. Mushkolaj·C. Beeli·M. A. Chernikov·H. R. Ott
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Abstract

We report the results of measurements of $^{27}$Al and $^{55}$Mn NMR spectra, the related spin-lattice relaxation rates, and the dc magnetic susceptibility of the stable decagonal quasicrystal Al$_{69.8}$Pd$_{12.1}$Mn$_{18.2}$. The temperature-variation of the magnetic susceptibility $χ(T)$ reveals that the Mn ions carry only an average magnetic moment of approximately $2μ_{\mathrm{B}}$, and confirms a spin-glass type freezing of the Mn-moments at $T_f=12$K. The NMR spectra reveal two partially resolved lines for the $^{27}$Al-nuclei, indicating that there are two different sets of environments for the Al-sites. The integrated intensity of the Mn line in the spectra suggests that about half of the Mn ions carry no magnetic moment. Below 50K, and upon decreasing the temperature, the $^{27}$Al NMR-linewidth $w$ and the spin-lattice relaxation rate $T_1^{-1}$ both grow with an increasingly negative slope, as it is often observed and interpreted as a critical "slowing down" of magnetic moments in systems approaching a spin-glass transition. Various features, such as a broad maximum in $T_1^{-1}(T)$ and a slope change in the $w(χ)$ plot, both around 120K, suggest a gradual reduction of the number of Mn moments with decreasing temperature below 120K.

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D. Rau, J. L. Gavilano, Sh. Mushkolaj, C. Beeli, M. A. Chernikov, H. R. Ott. 2003-04-11. Inhomogeneous magnetism in decagonal Al$_{69.8}$Pd$_{12.1}$Mn$_{18.1}$. https://doi.org/10.1103/physrevb.68.134204

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