Search

In this article, we report synthesis and magneto-transport analysis of Ni substituted Bi2Se3 crystals. Phase purity and crystalline growth are checked through X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Substitution of smaller Ni atoms is evident from lattice parameters which are apparently decreased with increased Ni concentration. Electron Dispersive X-ray analysis (EDAX) confirms presence of Ni atoms and Raman Spectroscopy measurements shows the presence of vibrational modes of Bi2Se3 with slight shift due to Ni substitution. Interestingly, Bi2Se3 tends to change its metallic phase to semiconducting phase with gradual Ni substitution. Magneto-resistance is also found to be drastically suppressed with Ni substitution due to semiconducting behavior of Ni substituted Bi2Se3. Magneto-conductivity of Ni substituted Bi2Se3 crystal is analyzed for the first time in this article by applying Hikami-Larkin-Nagaoka (HLN) model. [ABSTRACT FROM AUTHOR]

Here, we report the growth and characterization of single crystals of NdxSb2-xTe3 (x = 0 and 0.1), by solid-state reaction route via self-flux method. The phase and layered growth are confirmed through X-ray diffraction and scanning electron microscopy respectively. A slight contraction in lattice parameters is seen after Nd doping. Also a minute shift in vibrational modes of recorded Raman spectra has been observed by doping of Nd in Sb2Te3. The magneto-resistance values under magnetic field of 5 Tesla for Sb2Te3 are 75% at 2.5 K and 60% at 20 K, but only 40% at 5 K for Nd0.1Sb1.9Te3. DC magnetic measurements exhibit expected diamagnetic and paramagnetic behaviors for pure and Nd doped crystals respectively. A cusp-like behavior is observed in magneto-conductivity of both pure and Nd doped crystals at low magnetic fields (< 1 Tesla) which is analyzed using Hikami-Larkin-Nagaoka (HLN) model. For Sb2Te3, the fitted parameters α are −1.02 and −0.58 and the phase coherence lengths Lφ are 50.8(6)nm and 34.9(8)nm at temperatures 2.5 and 20 K respectively. For Nd0.1Sb1.9Te3, α is −0.29 and Lφ is 27.2(1)nm at 5 K. The α values clearly show the presence of weak anti-localization effect in both pure and Nd doped samples. Also with Nd doping, the contribution of bulk states increases in addition to conducting surface states in overall conduction mechanism. [ABSTRACT FROM AUTHOR]

We report the magneto-conductivity analysis at different temperatures under a magnetic field of up to 5 T of a well- characterized Bi2Te3 crystal. Details of crystal growth and various physical properties including high linear magneto-resistance are already reported by some of us. To elaborate upon the transport properties of Bi2Te3 crystal, the magneto-conductivity is fitted to the known Hikami-Larkin-Nagaoka (HLN) equation and it is found that the conduction mechanism is dominated by both surface-driven weak anti-localization (WAL) and the bulk weak localization (WL) states. The value of HLN equation coefficient (α) signifying the type of localization (WL, WAL or both WL and WAL) falls within the range of − 0.5 to − 1.5. In our case, the low-field (± 0.25 T) fitting of studied crystal exhibited a value of α close to − 0.86 for studied temperatures of up to 50 K, indicating both WAL and WL contributions. The phase coherence length (lφ) is found to decrease from 98.266 to 40.314 nm with increasing temperature. Summarily, the short letter reports the fact that bulk Bi2Te3 follows the HLN equation and quantitative analysis of the same facilitates to know the quality of studied crystal in terms of WAL to WL contributions and thus the surface to bulk conduction ratio. [ABSTRACT FROM AUTHOR]

Electrical resistivity studies reveal large granular effects in the superconductivity behaviour of the electron-doped cuprate, NdCeCuO, in polycrystalline form, much larger than their hole-doped counterparts. With the aim of investigating inter-granular coupling, as well as its variation with magnetic field and addition of Ag, AC susceptibility and magneto-resistance (MR) studies have been carried out on NdCeCuO + Ag composite system. A comparative study of the superconducting properties of the NdCeCuO + Ag composite system for Ag = 0, 5 and 15 wt%, including upper critical field [ H (0)], has been carried out and is presented. [ABSTRACT FROM AUTHOR]

In this letter, we report on the growth and characterization of bulk Bi Se single crystals. The studied Bi Se crystals are grown by the self-flux method through the solid-state reaction from high-temperature (950 °C) melt of constituent elements and slow cooling (2 ℃/h). The resultant crystals are shiny and grown in the [00l] direction, as evidenced from surface XRD. Detailed Reitveld analysis of powder X-ray diffraction (PXRD) of the crystals showed that these are crystallized in the rhombohedral crystal structure with a space group of R3m (D5), and the lattice parameters are a = 4.14 (2), b = 4.14 (2), and c = 28.7010 (7) Å. Temperature versus resistivity ( ρ− T) plots revealed metallic conduction down to 2 K, with typical room temperature resistivity ( ρ ) of around 0.53 m Ω-cm and residual resistivity ( ρ ) of 0.12 m Ω-cm. Resistivity under magnetic field [ ρ( T) H] measurements exhibited large + ve magneto-resistance right from 2 to 200 K. Isothermal magneto-resistance [ ρH] measurements at 2, 100, and 200 K exhibited magneto-resistance (MR) of up to 240 %, 130 %, and 60 %, respectively, at 14 T. Further, the MR plots are nonsaturating and linear with the field at all temperatures. At 2 K, the MR plots showed clear quantum oscillations at above say 10 T applied field. Also, the Kohler plots, i.e., Δ ρ/ ρ versus B/ ρ, were seen consolidating on one plot. Interestingly, the studied Bi Se single crystal exhibited the Shubnikov-de Haas (SdH) oscillations at 2 K under different applied magnetic fields ranging from 4 to 14 T. [ABSTRACT FROM AUTHOR]

Magnetic and magneto-transport properties of thin layers of the (Ga,Mn)(Bi,As) quaternary dilute magnetic semiconductor grown by the low-temperature molecular-beam epitaxy technique on GaAs substrates have been investigated. Ferromagnetic Curie temperature and magneto-crystalline anisotropy of the layers have been examined by using magneto-optical Kerr effect magnetometry and low-temperature magneto-transport measurements. Post-growth annealing treatment of the layers has been shown to enhance the hole concentration and Curie temperature in the layers. A significant increase in the magnitude of magneto-transport effects caused by incorporation of a small amount of Bi into the (Ga,Mn)As layers, revealed in the planar Hall effect (PHE) measurements, is interpreted as a result of enhanced spin-orbit coupling in the (Ga,Mn)(Bi,As) layers. A two-state behaviour of the planar Hall resistance at zero magnetic field provides its usefulness for applications in non-volatile memory devices. [ABSTRACT FROM AUTHOR]