Growth, Characterization and High-Field Magneto-Conductivity of Co0.1Bi2Se3 Topological Insulator

Abstract

We report the crystal growth as well as transport properties of Co added Bi 2 Se 3 (Co 0.1 Bi 2 Se 3 ) single crystals. The values of the lattice parameters a and b for Co added sample were observed to increase from a = b = 4.14(2) Å to 4.16(3) Å, whereas the c value decreased marginally from 28.70(3) Å to 28.69(5) as compared to the pure Bi 2 Se 3 . The Raman spectroscopy displayed higher Raman shift of corresponding A 1g 1 , Eg 2 and A 1g 2 vibrational modes for Co 0.1 Bi 2 Se 3 , and the resistivity curves with and without applied magnetic field shows a metallic behaviour. Both the crystals were subjected to magnetoresistance (MR) measurements under applied fields of 14Tesla. The value of MR is found to decrease from about 380% (5K, 14 Tesla) for Bi 2 Se 3 to 200% for Co 0.1 Bi 2 Se 3 . To elaborate the transport properties of pure and Co added Bi 2 Se 3 crystals, the magneto-conductivity is fitted to the HLN (Hikami Larkin Nagaoka) equation and it is found that the charge conduction is mainly dominated by surface driven WAL (weak anti-localization) with negligible bulk WL (weak localization) contribution in both crystals alike. The MH curves of Co 0.1 Bi 2 Se 3 crystal at different temperatures displayed a combination of both ferromagnetic and diamagnetic behaviour. On the other hand, the Electron Paramagnetic Resonance (EPR) revealed that pure Bi 2 Se 3 is diamagnetic whereas, Co orders ferro-magnetically with resonating field around 3422Oe at room temperature. The calculated value of Lande "g" factor is around 2.04 ± 0.05. Summarily, the short letter discusses the interesting magnetoconductivity and complex magnetism of Co in Co 0.1 Bi 2 Se 3 .

Structural, surface morphology and magneto-transport properties of self flux grown Eu doped Bi2Se3 single crystal

“…Furthermore, the elemental mapping for the Eu 0.1 Bi 1.9 Se 3 crystals [Figure 3 (c-e)] confirmed the homogeneous distribution of the constituent elements i.e., Eu, Bi and Se respectively, which is in accordance to their stoichiometric ratio. crystals are in agreement to our previously reported literature [44]. Furthermore, we can say that doping Bi 2 Se 3 with magnetic (Eu and Co) impurities results into lesser conductivity due to the breaking of TRS.…”

“…Here, we can say that Eu is substituted at Bi site and not in the Van der Waals Layer. Also, the situation is different than as for reported crystals are in agreement to our previously reported literature [44]. Furthermore, we can say that doping Bi 2 Se 3 with magnetic (Eu and Co) impurities results into lesser conductivity due to the breaking of TRS.…”

“…Figure 5 (a-b) displays the perpendicular magnetic field induced MR% for both pure (Bi 2 Se 3 ) and Eu doped Bi 2 Se 3 (Eu 0.1 Bi 1.9 Se 3 ) single crystals measured at varying temperatures (5 to 100K) and fields up to ± 5Tesla. Magneto-transport measurement schematic diagram is given in our own previous work on Co added Bi 2 Se 3 TI [44]. MR (%) is observed to decrease with increase in temperature from 5 to 100K, for both pure (Bi 2 Se 3 ) and Eu doped Bi 2 Se 3 (Eu 0.1 Bi 1.9 Se 3 ) single crystals [Fig.…”

“…High purity (99.99%, Alfa Aesar) bismuth (Bi), selenium (Se) and europium (Eu) were taken as the starting materials. Stoichiometric mixture (~1gram) of the starting materials were taken and sealed in an evacuated quartz tube (10 -3 Torr) as mentioned in our previously reported literature [44,47]. Briefly, the sealed quartz tube containing the rectangular pellet was kept inside an automated tube furnace and heated to 950˚C for 7.5hours (120˚C/hour).…”

“…There already exist some published reports on magnetically (Mn, Ni, Fe, Cr, V and Co) doped TIs, which focus on describing the effects of magnetic impurities, or discussing typical ferromagnetism on Dirac like conducting surface states in various TIs viz. Bi 2 Se 3 , Bi 2 Te 3 and Sb 2 Te 3 [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]. Till date, a very few reports have discussed on the magneto transport behaviour of Eu doped Bi 2 Se 3 thin films [45,46].…”