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A comprehensive study of selected properties of four (TiZrNbCu)1-xNix (x ≤ 0.25) amorphous high entropy alloys (a-HEA) has been performed. The samples were ribbons about 20 µm thick and their fully amorphous state was verified by X-ray diffraction and thermal analysis. The surface morphology, precise composition and the distribution of components were studied with a Scanning electron microscope (SEM) with an energy dispersive spectroscopy (EDS) attachment. The properties selected were the melting temperature (Tm), the low temperature specific heat (LTSH), the magnetic susceptibility χexp and the Young´s modulus (E). Whereas LTSH and χexp were measured for the as-cast samples, E was measured both for as-cast samples and relaxed samples (after a short anneal close to the glass transition temperature). The LTSH showed that the electronic density of states at the Fermi level, N0(EF), decreases with increasing x, whereas the Debye temperature (θD) increases with x. This is similar to what is observed in binary and ternary amorphous alloys of early transition metals (TE) with late transition metals (TL) and indicates that N0(EF) is dominated by the d-electrons of the TE.The LTSH also showed the absence of superconductivity down to 1.8K and indicated the emergence of the Boson peak above 4K in all alloys.The free-electron like paramagnetic contribution to χexp also decreases with x, whereas E, like θD, increases with x, indicating enhanced interatomic bonding on addition of Ni. The applicability of the rule of mixtures to these and other similar HEAs is briefly discussed.

A study of a transition from conventional multicomponent alloys to high-entropy alloys (HEAs) is important both for understanding the formation of HEAs and for proper evaluation of their potential with respect to that of conventional alloys. We report the main result of such a study performed on (TiZrNbNi)1−xCux metallic glasses (MG) over a broad concentration range x ≤ 0.52 encompassing both high-entropy-MGs and Cu-based MGs. A comprehensive study of the composition, homogeneity, thermal stability, atomic structure, electronic structure, and magnetic susceptibility of 11 alloys has been performed. Thermal analysis revealed a rather weak variation of thermal parameters and glass forming ability with x. The study of the atomic structure showed a linear variation of average interatomic distances and atomic volumes close to those predicted by Vegard's law. The coordination numbers and atomic packing fractions were constant throughout the explored concentration range. The electronic density of states (DOS) showed a split-band structure with DOS close to the Fermi level dominated with d-states of Ti, Zr, and Nb. Accordingly, magnetic susceptibility decreased linearly with x and extrapolated to that of Cu. Thus, the studied alloys show ideal solution behavior similar to that of binary Cu-Ti, Zr, and Hf MGs. The results are compared with those for (TiZrNbCu)1−xNix MGs and (CrMnFeCo)1−xNix alloys and their impact on understanding the transition from high-entropy-MGs to conventional MGs with the same composition is briefly discussed.

Understanding the formation of bulk metallic glasses (BMG) in metallic systems and finding a reliable criterion for selection of BMG compositions are among the most important issues in condensed matter physics and material science. Using the results of magnetic susceptibility measurements performed on both amorphous and crystallized Cu-Hf alloys (30-70 at% Cu) we find a correlation between the difference in magnetic susceptibilities of corresponding glassy and crystalline alloys and the variation in the glass forming ability (GFA) in these alloys. Since the same correlation can be inferred from data for the properties associated with the electronic structure of Cu-Zr alloys, it seems quite general and may apply to other glassy alloys based on early and late transition metals. This correlation is plausible from the free energy considerations and provides a simple way to select the compositions with high GFA.

The anion radicals with nonaromatic p-systems, such as semiquinones, are interesting in the design of functional materials. Magnetic properties of solvates of alkali salts of tetrachlorosemiquinone (chloranil) radical anion are tuned by crystal engineering using different solvents (2-butanone and acetonitrile) and/or cations (potassium and ammonium) in crystals. The structural and magnetic characteristics of two salts were studied by variable-temperature single crystal X-ray diffraction and magnetic susceptibility measurements. DFT and CAS-MP2 calculations were used to correlate magnetic and structural properties of radical anions. The solid-state structure of potassium tetrachlorosemiquinone 2-butanone solvate, influenced by temperature, switches between a paramagnetic-like monomeric radical form at high temperature (200 K) and diamagnetic dimeric one at low temperature (100 K). The reversible transition is controlled by solvent and cation types which affect intrastack distance and magnetic properties.