Defence Metallurgical Research Laboratory

About: Defence Metallurgical Research Laboratory is a facility organization based out in Hyderabad, India. It is known for research contribution in the topics: Microstructure & Alloy. The organization has 1208 authors who have published 2662 publications receiving 51663 citations.

Origin of spin gapless semiconductor behavior in CoFeCrGa: Theory and Experiment

Abstract: Despite a plethora of materials suggested for spintronic applications, a new class of materials has emerged, namely spin gapless semiconductors (SGS), which offers potentially more advantageous properties than existing ones These magnetic semiconductors exhibit a finite band gap for one spin channel and a closed gap for the other Here, supported by electronic-structure calculations, we report evidence of SGS behavior in equiatomic quaternary CoFeCrGa, having a cubic Heusler (prototype LiMgPdSn) structure but exhibiting chemical disorder (${\mathrm{DO}}_{3}$ structure) CoFeCrGa is found to transform from SGS to half-metallic phase under pressure, which is attributed to unique electronic-structure features The saturation magnetization $({M}_{S})$ obtained at $8\phantom{\rule{016em}{0ex}}\mathrm{K}$ agrees with the Slater-Pauling rule and the Curie temperature $({T}_{C})$ is found to exceed $400\phantom{\rule{016em}{0ex}}\mathrm{K}$ Carrier concentration (up to $250\phantom{\rule{016em}{0ex}}\mathrm{K}$) and electrical conductivity are observed to be nearly temperature independent, prerequisites for SGS The anomalous Hall coefficient is estimated to be $185\phantom{\rule{016em}{0ex}}\mathrm{S}/\mathrm{cm}$ at $5\phantom{\rule{016em}{0ex}}\mathrm{K}$ Considering the SGS properties and high ${T}_{C}$, this material appears to be promising for spintronic applications

Identification of hot corrosion resistant MCrAlY based bond coatings for gas turbine engine applications

Abstract: In the current paper, an attempt has been made to identify hot corrosion resistant coatings which can produce a thermodynamically stable and inert oxide scale during exposure to a hot corrosion environment and thereby enhance the coating life significantly. The results obtained from hot corrosion tests of a variety of MCrAlY-type coatings with different alloying elements and traces of silicon and hafnium in the presence of sodium chloride and vanadium containing environments revealed that a NiCoCrAlY coating exhibits maximum life time among the coatings studied. The results also revealed that presence of trace elements in the coating reduces coating life significantly. Based on the results, a novel electrochemical mechanism has been proposed. It has been shown that the hot corrosion of protective coatings is an electrochemical phenomena and hence the electrochemical techniques appear to be quite useful in evaluating coatings for hot corrosion resistance.