Structural study of an amorphous NiZr2 alloy by anomalous wide angle X-ray scattering and Reverse Monte Carlo simulations

The local atomic structure of an amorphous NiZr2 alloy was investigated using the anomalous wide-angle x-ray scattering (AWAXS), differential anomalous scattering (DAS) and reverse Monte Carlo (RMC) simulations techniques. The AWAXS measurements were performed at eight different incident photon energies, including some close to the Ni and Zr K edges. From the measurements eight total structure factor S(K,E) were derived. Using the AWAXS data four differential structure factors DSFi(K,Em,En) were derived, two about the Ni and Zr edges. The partial structure factors SNi-Ni(K), SNi-Zr(K) and SZr-Zr(K) were estimated by using two different methods. First, the S(K,E) and DSFi(K,Em,En) factors were combined and used in a matrix inversion process. Second, three S(K,E) factors were used as input data in the RMC technique. The coordination numbers and interatomic distances for the first neighbors extracted from the partial structure factors obtained by these two methods show a good agreement. By using the three-dimensional structure derived from the RMC simulations, the bond-angle distributions were calculated and they suggest the presence of distorted triangular-faced polyhedral units in the amorphous NiZr2 structure. We have used the Warren chemical short-range order parameter to evaluate the chemical short-range order for the amorphous NiZr2 alloy and for the NiZr2 compound. The calculated values show that the chemical short-range order found in these two materials is similar to that found in a solid solution.Comment: Submitted to Phys. Rev. B, 8 figure

Investigation of the ferromagnetic order in crystalline and amorphous Fe2Zr alloys

We present the study of the ferromagnetic behaviour of crystalline and amorphous samples with identical composition Fe2Zr. The crystalline sample was obtained by arc melting. The two amorphous samples were obtained by mechanical grinding from the intermetallic crystalline phase and by mechanical alloying starting from the elements, respectively. We investigated the magnetic properties of the alloy using Mössbauer spectroscopy and superconducting quantum interference device magnetometry. The values of the Mössbauer parameters are reported and discussed. We present the initial magnetization curves and hysteresis loops. The magnetization behaviour is marked by saturation at low field values with very small values of remanent magnetization and coercive field, indicating that the samples are soft ferromagnets; this feature is more sharpened in the crystal. The mechanically grinded sample is more similar to the crystalline compound than the mechanically alloyed sample

Can local order changes induce a phase transition in a liquid?

Neutron scattering measurements of the local order in ${\rm S}_{x}{\rm Te}_{1-x}$ mixtures were performed. Partial contributions to the first coordination shell were obtained by suitable modeling of the structure factors. Rapid changes in the local atomic environment are shown to be responsible for the closed-loop miscibility gap that occurs around x=0.4 at high temperature

Investigation of the ferromagnetic order in a crystalline Fe2Zr alloy

We present the study of the ferromagnetic behaviour of a crystalline Fe2Zr sample obtained by arc melting. Mossbauer spectroscopy measurements show that the sample is magnetically ordered at room temperature with ferromagnetic order. The magnetization behaviour obtained by superconducting quantum interference device magnetometry measurements indicates that the sample is a soft ferromagnet