TY - JOUR
T1 - Systematic Study of Ferromagnetism in CrxSb2−xTe3 Topological Insulator Thin Films using Electrical and Optical Techniques
AU - Singh, Angadjit
AU - Kamboj, Varun S.
AU - Liu, Jieyi
AU - Llandro, Justin
AU - Duffy, Liam B.
AU - Senanayak, Satyaprasad P.
AU - Beere, Harvey E.
AU - Ionescu, Adrian
AU - Ritchie, David A.
AU - Hesjedal, Thorsten
AU - Barnes, Crispin H.W.
N1 - Funding Information:
A.S. and V.K., acknowledge support from the SGPC Cambridge Commonwealth Trust (CCT). V.K., H.E.B., and D.A.R. acknowledge financial support from the Engineering and Physical Sciences Research Council (EPSRC) (Grant No. EP/J017671/1, Coherent Terahertz Systems, Grant No. EP/P021859/1, HyperTerahertz). T.H. acknowledges financial support from the John Fell Oxford University Press Research Fund and thanks RCaH for their hospitality. L.B.D. would like to acknowledge the financial support from EPSRC and the Science and Technology Facilities Council (UK). J.Llandro and C.H.W.B. are grateful for financial support from EPSRC (Grant No. EP/J00412X/1). A.S. acknowledges useful discussions with Dr Stuart Holmes. S.P.S. acknowledges funding from The Royal Society through the Newton International Fellowship.
PY - 2018/12/1
Y1 - 2018/12/1
N2 - Ferromagnetic ordering in a topological insulator can break time-reversal symmetry, realizing dissipationless electronic states in the absence of a magnetic field. The control of the magnetic state is of great importance for future device applications. We provide a detailed systematic study of the magnetic state in highly doped CrxSb2−xTe3 thin films using electrical transport, magneto-optic Kerr effect measurements and terahertz time domain spectroscopy, and also report an efficient electric gating of ferromagnetic order using the electrolyte ionic liquid [DEME][TFSI]. Upon increasing the Cr concentration from x = 0.15 to 0.76, the Curie temperature (Tc) was observed to increase by ~5 times to 176 K. In addition, it was possible to modify the magnetic moment by up to 50% with a gate bias variation of just ±3 V, which corresponds to an increase in carrier density by 50%. Further analysis on a sample with x = 0.76 exhibits a clear insulator-metal transition at Tc, indicating the consistency between the electrical and optical measurements. The direct correlation obtained between the carrier density and ferromagnetism - in both electrostatic and chemical doping - using optical and electrical means strongly suggests a carrier-mediated Ruderman-Kittel-Kasuya-Yoshida (RKKY) coupling scenario. Our low-voltage means of manipulating ferromagnetism, and consistency in optical and electrical measurements provides a way to realize exotic quantum states for spintronic and low energy magneto-electronic device applications.
AB - Ferromagnetic ordering in a topological insulator can break time-reversal symmetry, realizing dissipationless electronic states in the absence of a magnetic field. The control of the magnetic state is of great importance for future device applications. We provide a detailed systematic study of the magnetic state in highly doped CrxSb2−xTe3 thin films using electrical transport, magneto-optic Kerr effect measurements and terahertz time domain spectroscopy, and also report an efficient electric gating of ferromagnetic order using the electrolyte ionic liquid [DEME][TFSI]. Upon increasing the Cr concentration from x = 0.15 to 0.76, the Curie temperature (Tc) was observed to increase by ~5 times to 176 K. In addition, it was possible to modify the magnetic moment by up to 50% with a gate bias variation of just ±3 V, which corresponds to an increase in carrier density by 50%. Further analysis on a sample with x = 0.76 exhibits a clear insulator-metal transition at Tc, indicating the consistency between the electrical and optical measurements. The direct correlation obtained between the carrier density and ferromagnetism - in both electrostatic and chemical doping - using optical and electrical means strongly suggests a carrier-mediated Ruderman-Kittel-Kasuya-Yoshida (RKKY) coupling scenario. Our low-voltage means of manipulating ferromagnetism, and consistency in optical and electrical measurements provides a way to realize exotic quantum states for spintronic and low energy magneto-electronic device applications.
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U2 - 10.1038/s41598-018-35118-8
DO - 10.1038/s41598-018-35118-8
M3 - Article
C2 - 30451885
AN - SCOPUS:85056717963
VL - 8
JO - Scientific Reports
JF - Scientific Reports
SN - 2045-2322
IS - 1
M1 - 17024
ER -