Analysis Of Magnetotransport Data Research Articles

The effect of Sn intercalation on the superconducting properties of 2H[sbnd]NbSe2

2HNbSe2 is known to be an archetype layered transitional metal dichalcogenide superconductor with a superconducting transition temperature of 7.3 K. In this article, we investigate the influence of Sn intercalation on superconducting properties of 2HNbSe2. Sn being nonmagnetic and having no outer shell d-electrons unlike transition metals, one naively would presume that its effect on superconducting properties will be very marginal. However, our magnetic and transport studies reveal a significant reduction of both superconducting transition temperature and upper critical field [Tc and BC2 (0)] upon Sn intercalation. With a mere 4 mole% Sn intercalation, it is observed that Tc and BC2 (0) get suppressed by ∼3.5 K and 3 T, respectively. Werthamer-Helfand-Hohenberg (WHH) analysis of magneto-transport data is performed to estimate BC2 (0). From the low temperature Raman scattering data in the normal phase of intercalated 2HNbSe2, it is inferred that the suppression of superconductivity cannot be ascribed to strengthening of charge density wave (CDW) ordering. Rather, the weakening of superconductivity is attributed to the observed increase of c-axis lattice parameter and the possible changes in the Fermi surface upon Sn intercalation.

Investigation of magnetic and magneto-transport properties of ferromagnetic-charge ordered core-shell nanostructures

In our present study, we address in detail the magnetic and magneto-transport properties of ferromagnetic-charge ordered core-shell nanostructures. In these core-shell nanostructures, well-known half metallic La0.67Sr0.33MnO3 nanoparticles (average particle size, ∼20 nm) are wrapped by the charge ordered antiferromagnetic Pr0.67Ca0.33MnO3 (PCMO) matrix. The intrinsic properties of PCMO markedly modify it into such a core-shell form. The robustness of the PCMO matrix becomes fragile and melts at an external magnetic field (H) of ∼20 kOe. The analysis of magneto-transport data indicates the systematic reduction of the electron-electron and electron-magnon interactions in the presence of an external magnetic field in these nanostructures. The pronounced training effect appears in this phase separated compound, which was analyzed by considering the second order tunneling through the grain boundaries of the nanostructures. Additionally, the analysis of low field magnetoconductance data supports the second order tunneling and shows the close value of the universal limit (∼1.33).

Magnetotransport in transparent single-wall carbon nanotube networks

An experimental study of the low temperature magnetotransport in optically transparent single-wall carbon nanotube (SWNT) networks is reported. The SWNT network shows Coulomb gap variable-range hopping conduction at low temperatures. The magnetoresistance (MR) involves the interplay of two phenomena: a forward interference process leading to negative MR together with shrinkage of electronic wave function contributing to the positive MR. These two mechanisms fit the low-field data. The analysis of magnetotransport data gives an estimate for intrinsic parameters including localization length and Coulomb gap. The temperature dependence of the forward interference mechanism is shown to follow an inverse power-law dependence with an exponent close to 1, indicating the weak scattering process involved in the transport.

Migration of Si IN δ-doped GaAs and Al xGa 1 − x As: Effect of substrate temperature

We have investigated the effect of substrate temperature, T S, during growth by molecular beam epitaxy on the migration of Si atoms in δ- (or planar) doped GaAs and Al 0.25Ga 0.75As. Determinations of the extent of Si migration were made through analysis of quantum oscillations in the magnetoresistance and independently by using secondary ion mass spectroscopy (SIMS). Analysis of magnetotransport data in δ-doped GaAs samples indicates that there is negligible spread in structures grown at T S⩽530 °C, while in structures grown at higher T S there is a measurable spread which increases with T S. For T S=640 °C, the Si spread is determ be = 180 Å. A similar analysis performed on the magnetoresistance of δ-doped Al 0.25Ga 0.75As samples reveals that the Si spreads further in Al 0.25Ga 0.75As than in GaAs (for a comparable T S). SIMS measurements performed on the same structures confirm these findings.