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Synthesis: Complex intermetallic phases in the Al-Pd-Ru and Al-Pd-Ir alloy system


Known to date binary and ternary alloy systems of aluminium with platinum metals (Ru, Rh, Pd, Os, Ir and Pt) usually contain structurally complex intermetallics, including stable ternary quasicrystals. The title ternary alloy systems, studied for the first time, are linked to either Al-Pd-Fe (Ru and Fe belong to the same column in the periodic table) or Al-Pd-Co and Al-Pd-Rh (Co, Rh and Ir belong to the same column in the periodic table) previously also studied by PGI-5.

Based on the updates of the Al-Ru and Al-Ir constitutional diagrams the Al-rich parts of the Al-Pd-Ru and Al-Pd-Ir constitutional diagrams were determined in the temperature range up to 1100 C. The study was carried out using powder XRD, DTA, SEM/EDX and TEM. Both alloy systems exhibit formation of complex intermetallic phases.

 Annual Report 2008 (PDF, 688 kB)

Synthesis: Magnetic memory effect in complex metallic alloy T-Al-Mn-Pd


The most prominent example of magnetically frustrated systems are spin glasses (SGs). A SG is a site-disordered spin system that is frustrated and spatially disordered in the sense that the spins are positioned randomly in the sample. These two properties lead to highly degenerate free-energy landscapes with a distribution of barriers between different metastable states, resulting in broken ergodicity. Typical SGs are dilute magnetic alloys of noble metal hosts (Cu, Ag, Au) with magnetic impurities (Fe, Mn), the so-called canonical spin glasses. In this paper we show that pronounced broken-ergodicity phenomena are present also in a class of ordered complex intermetallic Taylor phases T-Al3Mn, T-Al3(Mn,Pd) and T-Al3(Mn,Fe).

The Taylor-phase T-Al3Mn,T-Al3(Mn,Pd) and TAl3(Mn,Fe) series of complex intermetallic compounds, belong to the class of magnetically frustrated spin systems that exhibit rich out of equilibrium spin dynamics in the nonergodic phase below the spin–freezing temperature Tf . We observe a memory effect in these materials: The spin structure of the material stores information on isothermal aging steps carried out during zero-field cooling, which is detected by measuring the magnetisation of the sample.

 Annual Report 2008 (PDF, 470 kB)

Synthesis: Novel type of metadislocations in the complex metallic alloy Al-Pd-Fe


Among the group of complex metallic alloys (CMAs), materials which feature a few hundreds of even thousands of atoms per unit cell, the so-called " epsilon-type phases are one of the most fascinating. Several structurally related orthorhombic phases have been identified and are denoted "l (l = 6, 16, 22, 28, 34) according to the index of the strong (0 0 l) reflection. They are ternary extensions of the binary Al3Pd phase in the Al-Pd-(Mn, Fe) alloy systems. epsilon-type phases are also found in the alloy systems Al- Pd-(Rh, Re, Ru, Co, Ir) and Al-Rh-(Ru, Cu, Ni).

We report on the observation of new variants of metadislocations in the orthorhombic complex metallic alloy phase Al-Pd-Fe. At Fe contents above about 3 at.% we find a novel type of metadislocation in the -structure, which has a complementary counterpart hosted in all epsilon-type phases possessing phason lines as structural elements.

 Annual Report 2007 (PDF, 1 MB)