Magnetic and transport properties of PrRhSi3
We have investigated the magnetic and transport properties of a noncentrosymmetric compound PrRhSi3 by dc magnetic susceptibility χ(T), isothermal magnetization M(H), thermoremanent magnetization M(t), specific heat Cp(T), electrical resistivity ρ(T,H) and muon spin relaxation (μSR) measurements. At low fields χ(T) shows two anomalies near 15 and 7 K with an irreversibility between ZFC and FC data below 15 K. In contrast, no anomaly is observed in Cp(T) or ρ(T) data. M(H) data at 2 K exhibit very sharp increase below 0.5 T and a weak hysteresis. M(t) exhibits very slow relaxation, typical for a spin-glass system. Even though the absence of any anomaly in Cp(T) is consistent with the spin-glass type behavior, there is no obvious origin of spin-glass behavior in this structurally well ordered compound. The crystal electric field (CEF) analysis of Cp(T) data indicates a CEF-split singlet ground state lying below a doublet at 81(1) K and a quasi-triplet at 152(2) K. The ρ(T) data indicate a metallic behavior, and ρ(H) exhibits a very high positive magnetoresistance, as high as ∼300% in 9 T at 2 K. No long range magnetic order or spin-glass behavior was detected in a μSR experiment down to 1.2 K.
Heat capacity of single-crystal La2CuO4 and polycrystalline La2-xSrxCuO4 (0 <= x <= 0.20) from 110 to 600 K.
Heat-capacity {ital C}({ital T}) data on the title materials, as well as on CuO for comparison, were obtained with use of a differential scanning calorimeter to a precision of {congruent}0.1--1%. The measurements were carried out (i) to characterize the thermal anomaly at the tetragonal-orthorhombic transition temperature {ital T}{sub 0} of single-crystal La{sub 2}CuO{sub 4} and polycrystalline La{sub 2{minus}{ital x}}Sr{sub {ital x}}CuO{sub 4} (0{le}{ital x}{le}0.20) and (ii) to search for thermal anomalies at the Neel temperature {ital T}{sub {ital N}} of La{sub 2}CuO{sub 4} ({congruent}300 K). We find a cusp-shaped anomaly with a peak at 523 K ({approx}{ital T}{sub 0}) for a single crystal of La{sub 2}CuO{sub 4} with {ital T}{sub {ital N}}=304 K and find the transition to be second order, consistent with previous neutron- and x-ray-diffraction measurements. {ital T}{sub {ital N}} was determined from measurements of the anisotropic magnetic susceptibility on the same crystal, which are also presented. The {ital C}({ital T}) anomaly at {ital T}{sub 0} is smeared out somewhat in polycrystalline La{sub 2}CuO{sub 4}.
Finite Difference Modeling on the Temperature Field of Substrate in Friction Surfacing
Friction surfacing is an advanced process of great potential, especially in the field of repair and reclamation of worn and damaged components. As a kind of thermal processing technology, the temperature profile and changes of the substrate in friction surfacing are important factors to get coatings of high quality. In this paper, the temperature field of the substrate during the process is simulated by finite difference method. The results are consistent with experiments, reappearing the temperature change of the substrate during friction surfacing, allowing further study on figuration and quality of coatings.