Magnetic behavior of (Al,Ge)65CuMn quaternary alloy quasicrystals
TL;DR: In this article, Tsai et al. reported the results of field and temperature dependent magnetization measurements on (Al,Ge)65CuMn quasicrystalline samples with ∼22 and 24 at.
Abstract: We report the results of field and temperature dependent magnetization measurements on (Al,Ge)65CuMn quasicrystalline samples with ∼22 and 24 at. % Mn. The Ge content is also kept ∼25 at. %. The data for these samples are then compared with the data taken on samples with low Ge content (∼10 and 0 at. %). Al40Ge25Cu10Mn25, a composition very close to one of the alloys studied here, is reported [Tsai et al., Jpn. J. Appl. Phys., 27, L2252 (1988)] in literature as a ferromagnetic, icosahedral QC with large TC. The detailed magnetic studies described here prove that the magnetism observed in these quaternary alloys is highly disordered. The two important observations made in our studies are (i) observation of short-range ferromagnetism in samples with high Ge and high Mn content, up to very high fields (H=5 T) and (ii) oscillatory magnetization (or existence of multiple minima in the M-T curves) observed for the same samples for H⩾1 kOe.
Citations
More filters
TL;DR: In this paper, electrical resistivity and magnetic properties on Ni 52 Mn 26 Al 22 polycrystalline Heusler alloy were investigated in detail and the progress of transformation of this alloy was also followed by heat flux measurements.
14 citations
Journal Article•
TL;DR: In this article, Icosahedral quasi-crystals with coercivity at room temperature are found in rapidly solidified Al-Ge-Mn and Al-Cu-Ge -Mn alloys with compositions ranging form 20 to 25 at%Ge, 22.5 to 25%Mn, and 0 to 10%Cu.
Abstract: Icosahedral quasi-crystals with coercivity at room temperature are found in rapidly solidified Al-Ge-Mn and Al-Cu-Ge-Mn alloys with compositions ranging form 20 to 25 at%Ge, 22.5 to 25%Mn and 0 to 10%Cu. The highest Curie temperature is 533 K for Al52.5Ge22.5Mu25 and 467 K for Al40Cu10Ge25Mn25. The magnetization ( σ20) of the Al-Ge-Mn alloys in a field of 20 kOe at room temperature increases from 0.2 to 0.5 emu/g with increasing Ge and Mn contents and the coercivity (Hc) is in the range of 0.7 to 1.1 kOe. The replacement of Al by 10%Cu is found to bring about significant increases of σ20 and Hc to 3.9 emu/g and 1.8 kOe.
1 citations
References
More filters
99 citations
TL;DR: In this article, the dc magnetization, the low-field ac magnetic susceptibility, and the electrical resistivity of icosahedral quasicrystals were reported, showing that the dc magnetic susceptibility is isotropic within the experimental uncertainty.
Abstract: We report measurements of the dc magnetization, the low-field ac magnetic susceptibility, and the electrical resistivity of large (up to 0.5 ${\mathrm{cm}}^{3}$) single-grain samples of icosahedral $R\ensuremath{-}\mathrm{M}\mathrm{g}\ensuremath{-}\mathrm{Z}\mathrm{n}$ $(R=\mathrm{Y},$ Tb, Dy, Ho, and Er). The dc magnetization and ac magnetic susceptibility data both indicate that icosahedral Tb-Mg-Zn and Dy-Mg-Zn undergo a transition to a spin-glass state at ${T}_{f}=5.8$ and 3.6 K, respectively, while low-temperature ac susceptibility measurements show that ${T}_{f}=1.95$ and 1.3 K for Ho-Mg-Zn and Er-Mg-Zn, respectively. For the series of solid solutions $({\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Tb}}_{x})\ensuremath{-}\mathrm{M}\mathrm{g}\ensuremath{-}\mathrm{Z}\mathrm{n},$ the freezing temperature ${T}_{f}$ varies approximately as ${x}^{2/3}.$ The $({\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Gd}}_{x})\ensuremath{-}\mathrm{M}\mathrm{g}\ensuremath{-}\mathrm{Z}\mathrm{n}$ solid solutions have lower ${T}_{f}$ values than $({\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Tb}}_{x})\ensuremath{-}\mathrm{M}\mathrm{g}\ensuremath{-}\mathrm{Z}\mathrm{n}$ for the same magnetic rare-earth concentrations (x), indicating that local moment anisotropy caused by crystalline electric-field effects plays a significant role in increasing ${T}_{f}.$ On the other hand, angular-dependent studies show that the dc magnetization for $Tg{T}_{f}$ is isotropic within the experimental uncertainty. The electrical resistivity $\ensuremath{\rho}(T)$ of the single-grain samples is only weakly temperature dependent, with a small, negative $d\ensuremath{\rho}/dT.$ Absolute values of the resistivity fall in the range between 150 and 200 \ensuremath{\mu}\ensuremath{\Omega} cm, which is distinctly lower than the values previously reported for other thermodynamically stable icosahedral quasicrystals.
92 citations
TL;DR: In this article, Icosahedral quasi-crystals with coercivity at room temperature are found in rapidly solidified Al-Ge-Mn and Al-Cu-Ge -Mn alloys with compositions ranging form 20 to 25 at%Ge, 22.5 to 25%Mn, and 0 to 10%Cu.
Abstract: Icosahedral quasi-crystals with coercivity at room temperature are found in rapidly solidified Al-Ge-Mn and Al-Cu-Ge-Mn alloys with compositions ranging form 20 to 25 at%Ge, 22.5 to 25%Mn and 0 to 10%Cu. The highest Curie temperature is 533 K for Al52.5Ge22.5Mu25 and 467 K for Al40Cu10Ge25Mn25. The magnetization ( σ20) of the Al-Ge-Mn alloys in a field of 20 kOe at room temperature increases from 0.2 to 0.5 emu/g with increasing Ge and Mn contents and the coercivity (Hc) is in the range of 0.7 to 1.1 kOe. The replacement of Al by 10%Cu is found to bring about significant increases of σ20 and Hc to 3.9 emu/g and 1.8 kOe.
62 citations
TL;DR: In this article, it is proposed that descriptions of the decagonal phase by analogy to an icosahedral axial system be abandoned and that a different six-axis system be adopted instead.
Abstract: From a quenched, melt-spun ribbon of a specimen of Al76Mn24, bulk composition, the decagonal phase and a closely related ‘Al3Mn’ phase have been examined using analytical electron microscopic techniques. It is proposed that descriptions of the decagonal phase by analogy to an icosahedral axial system be abandoned and that a different six-axis system be adopted instead, and that the non-crystallographic space group previously proposed for the decagonal phase be changed to one containing glide planes. The ‘Al3Mn’ phase is seen to be an extremely close relative of the Al-Mn decagonal phase. However, the state of knowledge about the ‘Al3Mn’ structure is too poor to be of any use in improving the understanding of atomic arrangements in the Al-Mn decagonal phase.
62 citations
TL;DR: In this paper, a single-phase icosahedral powder of the system Al74Si5Mn21 and its modification by isomorphous substitution on the Mn sites were determined from their Qperpendicular to -dependences within a strip-projection approach.
Abstract: Neutron diffraction data were obtained from a single-phase icosahedral powder of the system Al74Si5Mn21 and its modification by isomorphous substitution on the Mn sites Amplitudes and phase differences of the partial structure factors (FAl, FMn) were determined From their Qperpendicular to -dependences within a strip-projection approach, phases were reconstructed Atomic densities were then calculated in the physical space and in the six-dimensional periodic lattice, resulting in the first experimentally deduced decoration of the quasi-periodic network The Mackay icosahedron no longer appears as the necessary basic structural unit In six dimensions the structure has a simple CsCl-like space-group symmetry
58 citations