Pyoung-Kil Yoo

Spectroscopic Ellipsometry Studies of Cd1-xMnxTe Films Grown on GaAs

Spectroscopic ellipsometry measurements of the complex dielectric function of a series of Cd1-xMnxTe (0 ?x ?0.7) films grown on (100) GaAs by hot wall epitaxy have been performed in the 1.5?5.5 eV photon energy range at room temperature. The measured data were analyzed by fitting the second-derivative spectra (d2?/d?2) with a theoretical model, namely, the standard critical-point (SCP) line shapes. It was found that the SCP model explains the measured derivative spectra successfully. The composition dependence of the critical-point (CP) energies and Lorentzian broadening (?) was determined.

Martensite and spin-glass transition of a Cu-Zn-Al-Fe shape memory alloy single crystal

Summary form only given. In spite of many researches carried out on Cu-Zn-Al shape-memory alloys, only a few studies have been reported on the magnetic properties. We report that a quarternary Cu-Zn-A1-Fe single crystal simultaneously shows shape memory effect and spin glass behaviour. All the measurements have been made on a Cu-17.25 Zn-15.00 Al-1.00 Fe (at%) single crystal grown by Bridgman method with element purity more than 99.99% in vacuum-sealed quartz capsules. DC magnetization and magnetic hysteresis measurements were carried out using a commercial superconducting quantum interference device (SQUID) magnetometer in temperature range 8 /spl tilde/ 300 K and in applied magnetic fields ranging from 0 Oe to 20 kOe. The spontaneous measurements of electrical resistivity of complex impedance versus temperature was performed to determine the martensite starting temperature (M/sub s/). X-ray diffraction, SEM, EPMA and optical microscope were used to analyze the microstructure and the prepicitates.

Some quaternary CuZnAlNi shape memory alloys for MS below room temperature

In recent years the properties of the Cu-based shape-memory alloys have been extensively investigated by varying the composition, quenching condition, heat treatment, mechanical deformation and grain refinement of the alloys, which are of interest because of their low cost and easy fabrication. Mwamba and Delaey have shown the effect of Ni-content on the martensite starting temperature (M[sub s]) in Cu-Zn-Al-Ni alloys that have M[sub s] values above room temperature. The aim of the present paper is to determine the effect of Ni-content on M[sub s] in the ternary Cu-Zn-Al alloys for M[sub s] below room temperature.