Localized singlets and ferromagnetic fluctuations in the dilute magnetic topological insulator Sn0.95Mn0.05Te

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2020-04-01
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Vaknin, David
Pakhira, Santanu
Schlagel, Deborah
Islam, Farhan
Zhang, Jianhua
Pajerowski, D. M.
Wang, Cai-Zhuang
Johnston, David
McQueeney, Robert
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Schlagel, Deborah
Assistant Scientist III
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Physics and Astronomy
Physics and astronomy are basic natural sciences which attempt to describe and provide an understanding of both our world and our universe. Physics serves as the underpinning of many different disciplines including the other natural sciences and technological areas.
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Ames National LaboratoryPhysics and Astronomy
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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, Sn0.95Mn0.05Te, using inelastic neutron scattering. Neutron diffraction and magnetization data indicate that our Sn0.95Mn0.05Te sample has no FM long-range order above a temperature of 2 K. However, we observe slow, collective FM fluctuations (<70μeV), 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 JAF=460μeV. 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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