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arXiv · 1912.08268

Localized Singlets and Ferromagnetic Fluctuations in the Dilute Magnetic Topological Insulator Sn$_{0.95}$Mn$_{0.05}$Te

D. Vaknin·Santanu Pakhira·D. Schlagel·F. Islam·Jianhua Zhang·D. Pajerowski·C. Z. Wang·D. C. Johnston·R. J. McQueeney
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Abstract

The development of long-range ferromagnetic (FM) order in dilute magnetic topological insulators can induce dissipationless electronic surface transport via the quantum anomalous Hall effect. We measure the magnetic excitations in a prototypical magnetic topological crystalline insulator, Sn$_{0.95}$Mn$_{0.05}$Te, using inelastic neutron scattering. Neutron diffraction and magnetization data indicate that our Sn$_{0.95}$Mn$_{0.05}$Te sample has no FM long-range order above a temperature of 2 K. However, we observe slow, collective FM fluctuations ($<$~70 $μ$eV), indicating proximity to FM order. We also find a series of sharp peaks originating from local excitations of antiferromagnetically (AF) coupled and isolated Mn-Mn dimers with $J_{\rm AF}=460$~$μ$eV\@. The simultaneous presence of collective and localized components in the magnetic spectra highlight different roles for substituted Mn ions, with competition between FM order and the formation of AF-coupled Mn-Mn dimers.

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D. Vaknin, Santanu Pakhira, D. Schlagel, F. Islam, Jianhua Zhang, D. Pajerowski, C. Z. Wang, D. C. Johnston, R. J. McQueeney. 2019-12-17. Localized Singlets and Ferromagnetic Fluctuations in the Dilute Magnetic Topological Insulator Sn$_{0.95}$Mn$_{0.05}$Te. https://doi.org/10.1103/physrevb.101.140406

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