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.

We present measurements of the dielectric response of quasi one-dimensional (TMTTF) 2 AsF 6 in a wide temperature and frequency range. We provide a thorough characterization of the relaxational dynamics observed close to the ferroelectric-like transition at T c = 100 K. Our measurements, extending up to 100 MHz, reveal a continuous slowing down of the mean relaxation time when approaching T c from high as well as from low temperatures. The simultaneous critical rise of dielectric constant and relaxation time point to an explanation of the transition in terms of a classic ferroelectric scenario.

We present a detailed investigation of the low-frequency dielectric response of the charge-density-wave system ͑CDW͒ o-TaS 3 in wide temperature ͑5-300 K͒ and frequency ͑10 mHz to 100 MHz͒ ranges. Although our measurements agree relatively well with data performed in some restricted frequency and temperature ranges and previously published by several groups, we show that they do not correspond to a single lowfrequency process. Instead, three distinctive processes are found to contribute to the dielectric function below the CDW transition temperature. The temperature evolution of the characteristic relaxation time of the three processes bears a close resemblance to the phenomenology of the dielectric response of glasses. The freezing of some of these processes at finite temperatures leads to changes in the CDW properties, as is thoroughly documented in the literature. Based on these results, we propose a consistent model of the temperature evolution of the CDW ground state.

Recent studies (J. Alloys Compd. 695 (2017) 2661) of the electronic structure and properties of (TiZrNbCu) 1-x Ni x (x ≤ 0.25) amorphous high entropy alloys (a-HEA) have been extended to x = 0.5 in order to compare behaviours of a-HEA and conventional Ni-base metallic glasses (MG). The amorphous state of all samples was verified by thermal analysis and X-ray diffraction (XRD). XRD indicated a probable change in local atomic arrangements, i.e. short-range-order (SRO) for x ≥ 0.35.Simultaneously, thermal parameters, such as the first crystallization temperature T x and the liquidus temperature showed a tendency to saturate for x ≥ 0.35. The same tendency also appeared in the magnetic susceptibility χ exp and the linear term in the low temperature specific heat γ. The Debye temperatures and Young´s moduli also tend to saturate for x ≥ 0.35. These unusual changes in SRO and all properties within the amorphous phase seem correlated with the change of valence electron number (VEC) on increasing x.