1. Abstract Results Summary
Transport Property of Chromium-Doped
Bismuth Antimony Telluride Nanofilms
Qingyan Fan, Bin Li,，Zhenghua An, Shan Qiao
Institute of Advanced Materials and State Key Laboratory of Surface Physics, Fudan University, Shanghai , PR China
Localization Property and Ferromagnetism
Abstract
We report results of transport property of mechanically exfoliated single-crystal Chromium-Doped Bismuth Antimony Telluride nano films . It is found that the ferromagnetism depend on density of carriers which is different from the results of ultrathin films grown by molecular beam epitaxy .In addition we investigate the complex dependence of resistance on temperature, magnetic field to interpret the relation between carrier-mediated interactions and carriers' localization.
(a) Temperature dependent longitudinal resistance Rxx of the films Cr0.2Sb1.44Bi0.36Te3 . (b) Magnetic field dependent Hall resistance Rxy of the films at different temperatures. (c) Magnetoresistance of the films as a perpendicular magnetic field is applied above the Curie temperature (TC) . (d) Raw data of magnetoresistance of the films as a perpendicular magnetic field is applied below the Curie temperature (TC) .
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Results
Sample Preparation
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(a) SEM image of nanoplates on a 300nm SiO2 substrate. (b) The thicknesses of a plate in nanometer ,measured by Dektak 150.
Electrical and Magnetic Properties
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Dependence of Curie temperature (red) and Tm (blue) on Bi content (x). Error bars represent temperature spacing in RAH-T and Rxx-T measurements.
(a) Magnetic and electric properties of Cr-doped Sb1.8Bi0Te3 films . (b) Magnetic field dependent Hall resistance Ryx of the Cr0.2Sb1.8Bi0Te3 films at different temperatures. Temperature dependent longitudinal resistance Rxx of the films
Summary
We report results of transport property of mechanically exfoliated single-crystal Chromium-Doped Bismuth Antimony Telluride nano films .The ferromagnetic state was confirmed by the presence of the anomalous Hall effect. The Curie temperature is proportional to the density of holes which might suggest that the RKKY interaction is at play in the bulk state of the sample . The resistance maximum and the associated negative magnetoresistance near the Curie temperature may be related to disorder-modified carrier-carrier interactions. These interactions account also for the low-temperature increase of resistance.
Curie temperature and Carrier Concentration
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References
[1] Ohno, Making Nonmagnetic Semiconductors Ferromagnetic, science
[2] TomaszDietl,  Interplay between carrier localization and magnetism in diluted magnetic and ferromagnetic,  J. Phys. Soc. Jpn. 77 (2008).
[3] Liu, Minhao el, Crossover between Weak Antilocalization and Weak Localization in a Magnetically Doped Topological Insulator. Phys.Rev.Lett
Anomalous Hall effect of the Cr0.2Sb(1.8-X)BixTe3 film at T=2K. Dependence of (a) carrier density and (b) Curie temperature (TC) on Bi content (x). Error bars represent temperature spacing in RAH-T measurements.