Current-driven magnetization switching in ferromagnetic bulk Rashba semiconductor (Ge,Mn)Te

Multiferroic materials with both ferroelectric and ferromagnetic orders provide a promising arena for the electrical manipulation of magnetization through the mutual correlation between those ferroic orders. Such a concept of multiferroics may expand to semiconductor with both broken symmetries of spatial inversion and time reversal, that is, polar ferromagnetic semiconductors. Here, we report the observation of current-driven magnetization switching in one such example, (Ge,Mn)Te thin films. The ferromagnetism caused by Mn doping opens an exchange gap in original massless Dirac band of the polar semiconductor GeTe with Rashba-type spin-split bands. The anomalous Hall conductivity is enhanced with increasing hole carrier density, indicating that the contribution of the Berry phase is maximized as the Fermi level approaches the exchange gap. By means of pulse-current injection, the electrical switching of the magnetization is observed in the (Ge,Mn)Te thin films as thick as 200 nm, pointing to the Rashba-Edelstein effect of bulk origin. The efficiency of this effect strongly depends on the Fermi-level position owing to the efficient spin accumulation at around the gap. The magnetic bulk Rashba system will be a promising platform for exploring the functional correlations among electric polarization, magnetization, and current.

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Magnetization switching induced by spin–orbit torque from Co2MnGa magnetic Weyl semimetal thin films

Applied Physics Letters ◽

10.1063/5.0037178 ◽

2021 ◽

Vol 118 (6) ◽

pp. 062402

Author(s):

Ke Tang ◽

Zhenchao Wen ◽

Yong-Chang Lau ◽

Hiroaki Sukegawa ◽

Takeshi Seki ◽

...

Keyword(s):

Thin Films ◽

Spin Orbit ◽

Magnetization Switching ◽

Weyl Semimetal

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In Situ Measurement and Control of the Fermi Level in Colloidal Nanocrystal Thin Films during Their Fabrication

The Journal of Physical Chemistry Letters ◽

10.1021/acs.jpclett.8b03283 ◽

2018 ◽

Vol 9 (24) ◽

pp. 7165-7172 ◽

Cited By ~ 5

Author(s):

Sebastian Volk ◽

Nuri Yazdani ◽

Olesya Yarema ◽

Maksym Yarema ◽

Deniz Bozyigit ◽

...

Keyword(s):

Thin Films ◽

Fermi Level ◽

In Situ Measurement ◽

And Control ◽

Measurement And Control

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Fermi Level and Magnetic GaMnN Thin Films

ECS Transactions ◽

10.1149/1.2753274 ◽

2019 ◽

Vol 3 (25) ◽

pp. 423-427

Author(s):

Nadia A. El-Masry ◽

F. Erdem Arkun ◽

Acar Berkman ◽

Amr Mahrous ◽

John M. Zavada ◽

...

Keyword(s):

Thin Films ◽

Fermi Level

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Role of Surface Band Gap Widening in Cu(In, Ga)(Se, S)2 Thin-Films for the Photovoltaic Performance of ZnO/CdS/Cu(In, Ga)(Se, S)2 Heterojunction Solar Cells

MRS Proceedings ◽

10.1557/proc-763-b8.8 ◽

2003 ◽

Vol 763 ◽

Cited By ~ 4

Author(s):

U. Rau ◽

M. Turcu

Keyword(s):

Thin Films ◽

Surface Layer ◽

Solar Cells ◽

Fermi Level ◽

Band Gap ◽

Photovoltaic Performance ◽

Heterojunction Solar Cells ◽

Fermi Level Pinning ◽

Device Efficiency

AbstractNumerical simulations are used to investigate the role of the Cu-poor surface defect layer on Cu(In, Ga)Se2 thin-films for the photovoltaic performance of ZnO/CdS/Cu(In, Ga)Se2 heterojunction solar cells. We model the surface layer either as a material which is n-type doped, or as a material which is type-inverted due to Fermi-level pinning by donor-like defects at the interface with CdS. We further assume a band gap widening of this layer with respect to the Cu(In, Ga)Se2 bulk. This feature turns out to represent the key quality of the Cu(In, Ga)Se2 surface as it prevents recombination at the absorber/CdS buffer interface. Whether the type inversion results from n-type doping or from Fermi-level pinning is only of minor importance as long as the surface layer does not imply a too large number of excess defects in its bulk or at its interface with the normal absorber. With increasing number of those defects an n-type layer proofs to be less sensitive to material deterioration when compared to the type-inversion by Fermi-level pinning. For wide gap chalcopyrite solar cells the internal valence band offset between the surface layer and the chalcopyrite appears equally vital for the device efficiency. However, the unfavorable band-offsets of the ZnO/CdS/Cu(In, Ga)Se2 heterojunction limit the device efficiency because of the deterioration of the fill factor.

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Skyrmions in Multiferroic Insulator

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314084526 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C1547-C1547

Author(s):

Shinichiro Seki

Keyword(s):

Present Finding ◽

Berry Phase ◽

High Energy ◽

Electric Polarization ◽

Orbit Interaction ◽

Nanometer Scale ◽

Metallic Materials ◽

Device Applications ◽

High Energy Efficiency ◽

Spin Texture

Magnetic skyrmion is a topologically stable particle-like object, which appears as nanometer-scale vortex-like spin texture in a chiral-lattice magnet [1]. In metallic materials (MnSi, FeGe, Fe1-xCoxSi etc), electrons moving through skyrmion spin texture gain a nontrivial quantum Berry phase, which provides topological force to the underlying spin texture and enables the current-induced manipulation of magnetic skyrmion [2]. Such electric controllability, in addition to the particle-like nature, is a promising advantage for potential spintronic device applications. Recently, we newly discovered that skyrmions appear also in an insulating chiral-lattice magnet Cu2OSeO3 [3]. We find that the skyrmions in insulator can magnetically induce electric polarization through the relativistic spin-orbit interaction, which implies possible manipulation of the skyrmion by external electric field without loss of joule heating. The present finding of multiferroic skyrmion may pave a new route toward the engineering of novel magnetoelectric devices with high energy efficiency. In this talk, our recent attempts to drive skyrmions by external field are also introduced.

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