Research Results – Synthesis by Sputtering Deposition and Crystal Growth
Synthesis: Complex Intermetallic Phases in the Al-Pd-Ru and Al-Pd-Ir Alloy System
All binary and ternary alloy systems of aluminium with platinum metals (Ru, Rh, Pd, Os, Ir and Pt) known to date usually contain structurally complex intermetallics, including stable ternary quasicrystals. The term “ternary alloy systems”, studied here for the first time, is 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 again belong to the same column in the periodic table) previously also studied by PGI-5.
Based on 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 of up to 1100 C. The study was carried out using powder XRD, DTA, SEM/EDX and TEM. Both alloy systems exhibit the formation of complex intermetallic phases.
Synthesis: Magnetic Memory Effect in Complex Metallic Alloy T-Al-Mn-Pd
The most prominent example of magnetically frustrated systems is spin glasses (SGs). An 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 non-ergodic 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.
Synthesis: Novel Type of Metadislocations in the Complex Metallic Alloy Al-Pd-Fe
Within the group of complex metallic alloys (CMAs), materials which feature a few hundreds or even a few thousands of atoms per unit cell, the so-called "epsilon-type” phases, are among the most fascinating. Several structurally related orthorhombic phases have been identified and are denoted as "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 approximately 3 %, 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.