The Sb 2 Te 3 crystals are grown using the conventional self flux method via solid state reaction route, by melting constituent elements (Sb and Te) at high temperature (850˚C), followed by slow cooling (2˚C/hour). As grown Sb 2 Te 3 crystals are analysed for various physical properties by X-ray diffraction (XRD), Raman Spectroscopy, Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (EDAX) and electrical measurements under magnetic field (6Tesla) down to low temperature (2.5K). The XRD pattern revealed the growth of synthesized Sb 2 Te 3 sample along (00l) plane, whereas the SEM along with EDAX measurements displayed the layered structure with near stoichiometric composition, without foreign contamination. The Raman scattering studies displayed known (A 1g 1 , E g 2 and A 1g 2 ) vibrational modes for the studied Sb 2 Te 3 . The temperature dependent electrical resistivity measurements illustrated the metallic nature of the as grown Sb 2 Te 3 single crystal. Further, the magnetotransport studies represented linear positive magneto-resistance (MR) reaching up to 80% at 2.5K under an applied field of 6Tesla.The weak anti localization (WAL) related low field (± 2Tesla) magneto-conductance at low temperatures (2.5K and 20K) has been analysed and discussed using the Hikami-Larkin -Nagaoka (HLN) model. Summarily, the short letter reports an easy and versatile method for crystal growth of bulk Sb 2 Te 3 topological insulator (TI) and its brief physical property characterization.
We report the magneto-conductivity analysis at different temperatures under magnetic field of up to 5Tesla of a well characterized Bi 2 Te 3 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 Bi 2 Te 3 crystal, the magneto conductivity is fitted to the known HLN (Hikami Larkin Nagaoka) equation and it is found that the conduction mechanism is dominated by both surface driven WAL (weak anti localization) and the bulk WL states. The value of HLN equation coefficient (⍺) 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 (±0.25Tesla) fitting of studied crystal exhibited value of ⍺ close to -0.86 for studied temperatures of up to 50K, indicating both WAL and WL contributions. The phase coherence length ( ) is found to decrease from 98.266 to 40.314nm with increasing temperature. Summarily, the short letter reports the fact that bulk Bi 2 Te 3 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.
Yttrium Iron Garnet (YIG) and bismuth (Bi) substituted YIG (Bi0.1Y2.9Fe5O12, BYG) films are grown in-situ on single crystalline Gadolinium Gallium Garnet (GGG) substrates [with (100) and (111) orientations] using pulsed laser deposition (PLD) technique. As the orientation of the Bi-YIG film changes from (100) to (111), the lattice constant is enhanced from 12.384 Å to 12.401 Å due to orientation dependent distribution of Bi3+ ions at dodecahedral sites in the lattice cell. Atomic force microscopy (AFM) images show smooth film surfaces with roughness 0.308 nm in Bi-YIG (111). The change in substrate orientation leads to the modification of Gilbert damping which, in turn, gives rise to the enhancement of ferromagnetic resonance (FMR) line width. The best values of Gilbert damping are found to be (0.54 ± 0.06) × 10−4, for YIG (100) and (6.27 ± 0.33) × 10−4, for Bi-YIG (111) oriented films. Angle variation (ϕ) measurements of the Hr are also performed, that shows a four-fold symmetry for the resonance field in the (100) grown film. In addition, the value of effective magnetization (4πMeff) and extrinsic linewidth (ΔH0) are observed to be dependent on substrate orientation. Hence PLD growth can assist single-crystalline YIG and BYG films with a perfect interface that can be used for spintronics and related device applications.
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