We have investigated the magnetic properties of highly anisotropic layered ferromagnetic semiconductor CrI3 under hydrostatic pressure with magnetic field along the easy-axis of magnetization. At ambient pressure, CrI3 undergoes a second-order paramagnetic to ferromagnetic phase transition at TC =60.4 K. TC is found to increase sublinearly from 60.4 to 64.9 K as pressure increases from 0 to 1.0 GPa. With the increase in pressure, the transition becomes sharper while magnetization at low-field decreases monotonically due to the decrease in magnetocrystalline anisotropy. The weak low-field anomaly at around 48 K, resulting from the two-step magnetic ordering, also shifts toward higher temperature with increasing pressure. The observed increase in TC and the decrease in magnetization could originate from change in coupling between the layers and Cr-I-Cr bond angle with pressure.
The impact of hydrostatic pressure (P) up to 1 GPa on Tc, Jc and the nature of the pinning mechanism in FexNbSe2 single crystals have been investigated within the framework of the collective theory. We found that the pressure can induce a transition from the regime where pinning is controlled by spatial variation in the critical transition temperature (δTc) to the regime controlled by spatial variation in the mean free path (δℓ). Furthermore, Tc and low field Jc are slightly induced, although the Jc drops more rapidly at high fields than at ambient P. The pressure effect enhances the anisotropy and reduces the coherence length, resulting in weak interaction of the vortex cores with the pinning centers. Moreover, the P can induce the density of states, which, in turn, leads to enhance in Tc with increasing P. P enhances the Tc with the rates of dTc/dP of 0.86, 1.35 and 1.47 K/GPa for FexNbSe2, respectively. The magnetization data are used to establish a vortex phase diagram. The nature of the vortices has been determined from the scaling behaviour of the pinning force density extracted from the Jc–H isotherms and demonstrates the point pinning mechanism.
Temperature and field dependence of magnetic measurements under hydrostatic pressure are carried out on a noncentrosymmetric superconductor α‐BiPd up to ≈1 GPa, and a 3D (temperature—magnetic field—pressure) phase diagram is reported for the first time. The experimental results are analyzed using various theoretical approaches, such as the Ginzburg–Landau formula, Bean's critical state model, Dew–Hughes model, and collective pinning theory, and several superconducting parameters are also estimated. Critical temperature, critical current density, and pinning force are decreased with the application of both pressure and magnetic field. It is observed that pressure diminishes the superconductivity moderately and changes the mean free path, which leads to crossover from the δTc pinning mechanism to δl type in α‐BiPd.
We report high pressure structural studies (52 GPa) at room temperature combined with magnetic [(M(T):1GPa] and electrical resistivity [(ρ(T):0-21GPa)] measurements down to 2K on Fe0.99Ni0.01Se0.5Te0.5 superconductor using designer diamond anvils (D-DAC) pressure cell. The M(T) data shows huge enhancement of superconducting transition temperature (Tc) from 8.62 to 14.8 K (1 GPa) and ρ(T) reveals maximum enhancement of Tc ~ 30.5 K at 3 GPa (dTc/dP= ~ 7.19 K/GPa) followed by moderate decrease of Tc up to 19 K at 7.5 GPa, further increasing pressure Tc gets vanished at 10.6 GPa. The reduction of Tc due to the occurrence of structural transition that is likely associated with possible reduction of charge carriers in the density of states in Fermi surface. The high pressure XRD measurements shows tetragonal phase exists up to 7 GPa, followed by mixed-phase which is visible between 7.5 GPa to 14.5 GPa. The structural transformation occurs at 15 GPa from tetragonal (P4/nmm) to NiAs -type hexagonal phase (P63/mmc) and it is stable up to 52 GPa were confirmed from the equation of state (EOS) and it can be correlated with variation of Tc under pressure for Fe0.99Ni0.01Se0.5Te0.5 chalcogenide superconductors.
Purpose The purpose of this paper is to investigate the use of embedded Shape Memory Alloy (SMA) nitinol wire for the enhancement of vibration and damping characteristics of filament-wound fiber-reinforced plastic composite hollow shafts. Design/methodology/approach The plain Glass Fiber-Reinforced Plastic (GFRP) and plain Carbon Fiber-Reinforced Plastic (CFRP) hollow shafts were manufactured by filament winding technique. Experimental modal analysis was conducted for plain hollow shafts of C1045 steel, GFRP and CFRP by subjecting them to flexural vibrations as per ASTM standard C747, with both ends clamped (C-C) end condition to investigate their vibration and damping behavior in terms of first natural frequency, damping time and damping ratio. Nitinol wires pre-stressed at various pre-strains (2, 4 and 6 per cent) were embedded with CFRP hollow shafts following same manufacturing technique, and similar experimental modal analysis was carried out by activating nitinol wires. The first natural frequencies of all the shaft materials were also predicted theoretically and compared with experimental measurements. Findings Among the three materials C1045 steel, plain GFRP and plain CFRP, the vibration and damping behavior were found to be the best for plain CFRP. Hence, CFRP shafts were considered for further improvement by embedding nitinol wires at pre-stressed condition. For CFRP shafts embedded with nitinol wires, the damping time decreased; and damping ratio and first natural frequency increased with increase in percentage of pre-strain. In comparison with plain CFRP, 7 per cent increase in first natural frequency and 100 per cent increase in damping ratio were observed for nitinol embedded CFRP shafts with 6 per cent pre-strain. Theoretical predictions of the first natural frequencies agree well with the experimental results for all the shaft materials. Originality/value The effect of nitinol on vibration and damping characteristics of filament wound hollow CFRP composite shafts with different pre-strains has not been studied extensively by the previous researchers. This paper addresses the effect of embedded nitinol wires pre-stressed at three varied pre-strains, that is, 2, 4 and 6 per cent on the vibration and damping characteristics of composite hollow CFRP shafts manufactured by filament winding technique.
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