Browsing by Author "Lu, L"

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    Stress/strain induced flux pinning in highly dense MgB2 bulks
    (Institute of Electrical and Electronics Engineers (IEEE), 2009-06-01) Zeng, R; Dou, SX; Lu, L; Li, WX; Poh, CK; Kim, JH; Horvat, J; Shi, DQ; Wang, JL; Munroe, P; Wang, XF; Zheng, RK; Ringer, SP; Rindfleisch, M; Tomsic, M
    We have systematically studied the flux pinning behavior of MgB(2) bulks synthesized by direct diffusion of Mg into pressed pellets of high purity crystalline B powder, with and without mixing with C and SiC nanoparticles, at a reaction temperature of 850 degrees C for 10 hrs. All of the samples showed very high purity and high density, but their microstructure and flux pinning behavior showed significant differences. It was found that the pure MgB(2) agrees with the delta T(c) pinning model, nano-C doped MgB(2) agrees with the delta l pinning model, while the SiC + MgB(2) composite agrees with the delta epsilon pinning model (stress/strain field pinning), since the dominant micro-defects that influence the flux pinning in these three samples are different. © 2009, Institute of Electrical and Electronics Engineers (IEEE)
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    Three first order magnetic phase transitions in re-entrant ferromagnet PrMn1.4Fe0.6Ge2
    (Elsevier, 2010-09-03) Zeng, R; Wang, JL; Lu, L; Li, WX; Campbell, SJ; Dou, SX
    Three first order magnetic phase transitions (FOMTs) have been detected and evaluated over the temperature range from 5 to 340 K at fields up to 9 T in PrMn1.4Fe0.6Ge2. All three FOMTs, from (with decreasing temperature) an antiferromagnetic (AFl) to a c-axis canted ferromagnetic (Fmc) state, to a c-axis canted antiferromagnetic (AFmc) state, and then to an Fmc state plus an additional Pr-sublattice magnetic contribution (Fmc + F(Pr)), exhibited temperature and field-induced transition features. A interesting phenomenon was observed, in that magnetic field can induce an AFmc to Fmc + F(Pr) transition, and then diminish and finally eliminate the re-entrant magnetic transition behavior under high field as well. Based on systematic measurements and analysis, a magnetic phase diagram has been determined. © 2010, Elsevier Ltd.