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arXiv · 1505.00728

Resonant magneto-optic Kerr effect in the magnetic topological insulator Cr:(Sb$_x$,Bi$_{1-x}$)$_2$Te$_3$

Shreyas Patankar·J. P. Hinton·Joel Griesmar·J. Orenstein·J. S. Dodge·Xufeng Kou·Lei Pan·Kang L. Wang·A. J. Bestwick·E. J. Fox·D. Goldhaber-Gordon·Jing Wang·Shou-Cheng Zhang
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Abstract

We report measurements of the polar Kerr effect, proportional to the out-of-plane component of the magnetization, in thin films of the magnetically doped topological insulator $(\text{Cr}_{0.12}\text{Bi}_{0.26}\text{Sb}_{0.62})_2\text{Te}_3$. Measurements of the complex Kerr angle, $Θ_K$, were performed as a function of photon energy in the range $0.8\text{ eV}<\hbarω<3.0\text{ eV}$. We observed a peak in the real part of $Θ_K(ω)$ and zero crossing in the imaginary part that we attribute to resonant interaction with a spin-orbit avoided crossing located $\approx$ 1.6 eV above the Fermi energy. The resonant enhancement allows measurement of the temperature and magnetic field dependence of $Θ_K$ in the ultrathin film limit, $d\geq2$ quintuple layers. We find a sharp transition to zero remanent magnetization at 6 K for $d<8$~QL, consistent with theories of the dependence of impurity spin interactions on film thickness and their location relative to topological insulator surfaces.

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Shreyas Patankar, J. P. Hinton, Joel Griesmar, J. Orenstein, J. S. Dodge, Xufeng Kou, Lei Pan, Kang L. Wang, A. J. Bestwick, E. J. Fox, D. Goldhaber-Gordon, Jing Wang, Shou-Cheng Zhang. 2015-12-02. Resonant magneto-optic Kerr effect in the magnetic topological insulator Cr:(Sb$_x$,Bi$_{1-x}$)$_2$Te$_3$. https://doi.org/10.1103/physrevb.92.214440

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