arXiv subjects

Cheng Song

Publications and source records attributed to Cheng Song.

46 records · Page 3Linked to original sources

arXiv2018

Observation of Anomalous Hall Effect in Noncollinear Antiferromagnetic Mn3Sn Films

Magnetotransport is at the center of the spintronics. Mn3Sn, an antiferromagnet that has a noncollinear 120° spin order, exhibits large anomalous Hall effect (AHE) at room temperature. But such a behavior has been remained elusive in Mn3Sn films. Here we report the observation of robust AHE up to room temperature in quasi-epitaxial Mn3Sn thin films, prepared by magnetron sputtering. The growth of both (11-20)- and (0001)-oriented Mn3Sn films provides a unique opportunity for comparing AHE in three different measurement configurations. When the magnetic field is swept along (0001) plane, such as the direction of [01-10] and [2-1-10] the films show comparatively higher anomalous Hall conductivity than its perpendicular counterpart ([0001]), irrespective of their respectively orthogonal current along [0001] or [01-10]. A quite weak ferromagnetic moment of 3 emu/cm^3 is obtained in (11-20)-oriented Mn3Sn films, guaranteeing the switching of the Hall signals with magnetization reversal. Our finding would advance the integration of Mn3Sn in antiferromagnetic spintronics.

cond-mat.mtrl-sci↗

arXiv2018

How to manipulate magnetic states of antiferromagnets

Antiferromagnetic materials, which have drawn considerable attention recently, have fascinating features: they are robust against perturbation, produce no stray fields, and exhibit ultrafast dynamics. Discerning how to efficiently manipulate the magnetic state of an antiferromagnet is key to the development of antiferromagnetic spintronics. In this review, we introduce four main methods (magnetic, strain, electrical, and optical) to mediate the magnetic states and elaborate on intrinsic origins of different antiferromagnetic materials. Magnetic control includes a strong magnetic field, exchange bias, and field cooling, which are traditional and basic. Strain control involves the magnetic anisotropy effect or metamagnetic transition. Electrical control can be divided into two parts, electric field and electric current, both of which are convenient for practical applications. Optical control includes thermal and electronic excitation, an inertia-driven mechanism, and terahertz laser control, with the potential for ultrafast antiferromagnetic manipulation. This review sheds light on effective usage of antiferromagnets and provides a new perspective on antiferromagnetic spintronics.

cond-mat.mtrl-sci↗

arXiv2017

Time resolved measurements of the switching trajectory of Pt/Co elements induced by spin-orbit torques

We report the experimental observation of spin-orbit torque induced switching of perpendicularly magnetized Pt/Co elements in a time resolved stroboscopic experiment based on high resolution Kerr microscopy. Magnetization dynamics is induced by injecting sub-nanosecond current pulses into the bilayer while simultaneously applying static in-plane magnetic bias fields. Highly reproducible homogeneous switching on time scales of several tens of nanoseconds is observed. Our findings can be corroborated using micromagnetic modelling only when including a field-like torque term as well as the Dzyaloshinskii-Moriya interaction mediated by finite temperature.

cond-mat.mtrl-sci↗

arXiv2017

Photon-gated spin transistor

Spin-polarized field-effect transistor (spin-FET), where a dielectric layer is generally employed for the electrical gating as the traditional FET, stands out as a seminal spintronic device under the miniaturization trend of electronics. It would be fundamentally transformative if optical gating was used for spin-FET. We report a new type of spin-polarized field-effect transistor (spin-FET) with optical gating, which is fabricated by partial exposure of the (La,Sr)MnO3 channel to light-emitting diode (LED) light. The manipulation of the channel conductivity is ascribed to the enhanced scattering of the spin-polarized current by photon-excited antiparallel aligned spins. And the photon-gated spin-FET shows strong light power dependence and reproducible enhancement of resistance under light illumination, indicting well-defined conductivity cycling features. Our finding would enrich the concept of spin-FET and promote the use of optical means in spintronics for low power consumption and ultrafast data processing.

cond-mat.mtrl-sci↗

arXiv2017

Recent progress in voltage control of magnetism: Materials, mechanisms, and performance

Voltage control of magnetism (VCM) is attracting increasing interest and exciting significant research activity driven by its profound physics and enormous potential for application. This review article aims to provide a comprehensive review of recent progress in VCM in different thin films. We first present a brief summary of the modulation of magnetism by electric fields and describe its discovery, development, classification, mechanism, and potential applications. In the second part, we focus on the classification of VCM from the viewpoint of materials, where both the magnetic medium and dielectric gating materials, and their influences on magnetic modulation efficiency are systematically described. In the third part, the nature of VCM is discussed in detail, including the conventional mechanisms of charge, strain, and exchange coupling at the interfaces of heterostructures, as well as the emergent models of orbital reconstruction and electrochemical effect. The fourth part mainly illustrates the typical performance characteristics of VCM, and discusses, in particular, its promising application for reducing power consumption and realizing high-density memory in several device configurations. The present review concludes with a discussion of the challenges and future prospects of VCM, which will inspire more in-depth research and advance the practical applications of this field.

cond-mat.mtrl-sci↗

arXiv2015

Electrical control of magnetism in oxides

This review article aims at illustrating the recent progresses in the electrical control of magnetism in oxides with profound physics and enormous potential applications. In the first part, we provide a comprehensive summary of the electrical control of magnetism in the classic multiferroic heterostructures and clarify their various mechanisms lying behind. The second part focuses on the novel route of electric double layer gating for driving a significantly electronic phase transition in magnetic oxides by a small voltage. The electric field applied on the ordinary dielectric oxide in the third part is used to control the magnetic phenomenon originated from the charge transfer and orbital reconstruction at the interface between dissimilar correlated oxides. At last, we analyze the challenges in electrical control of magnetism in oxides, both on mechanism and practical application, which would inspire more in-depth researches and advance the development in this field.

cond-mat.mtrl-sci↗

arXiv2015

Magnetoelectric coupling induced by interfacial orbital reconstruction

The magnetoelectric coupling effect with profound physics and enormous potential applications has provoked a great number of research activities in materials science. Here, we report that the reversible orbital reconstruction driven by ferroelectric polarization modulates the magnetic performance of ferroelectric ferromagnetic heterostructure. Mn in plane orbital occupancy and related interfacial exotic magnetic state are enhanced and weakened by the negative and positive electric field, respectively. Our findings thus not only present a broad opportunity to fill the missing member, orbital in the mechanism of magnetoelectric coupling, but also make the orbital degree of freedom straight forward to the application in microelectronic device.

cond-mat.str-el↗

arXiv2015

Electrical control of exchange spring in antiferromagnetic metals

Manipulation of antiferromagnetic (AFM) spins by electrical means is on great demand to develop the AFM spintronics with low power consumption. In spite of the electrical modulation of insulated AFMs through coupling between their intrinsic ferroelectricity and antiferromagnetism, direct electrical control of AFM metals remains challenging due to the screening effect by the surface charge, and the manipulation is confined to a limited depth of atomic dimensions, which is insufficient to form a stable AFM exchange spring. In the present letter we primarily report a reversible electrical control of exchange spring in AFM metals, using an ionic liquid to exert a substantial electric-field effect. The exchange spring could transfer the force to the ferromagnet/antiferromagnet interface, enabling a deeper modulation depth in AFM metals. The manipulation of AFM moments by gate voltage is demonstrated in [Co/Pt]/IrMn model system and a single IrMn layer with the IrMn thickness up to 5 nm. Besides the fundamental significance of modulating the spin structures in metallic AFM via all-electrical fashion, the present finding would advance the development of low-power-consumption AFM spintronics.

cond-mat.mtrl-sci↗

arXiv2014

Electrical manipulation of orbital occupancy and magnetic anisotropy in manganites

Electrical manipulation of lattice, charge, and spin has been realized respectively by the piezoelectric effect, field-effect transistor, and electric field control of ferromagnetism, bringing about dramatic promotions both in fundamental research and industrial production. However, it is generally accepted that the orbital of materials are impossible to be altered once they have been made. Here we use electric-field to dynamically tune the electronic phase transition in (La,Sr)MnO3 films with different Mn^4+/(Mn^3+ + Mn^4+) ratios. The orbital occupancy and corresponding magnetic anisotropy of these thin films are manipulated by gate voltage in a reversible and quantitative manner. Positive gate voltage increases the proportion of occupancy of the orbital and magnetic anisotropy that were initially favored by strain (irrespective of tensile and compressive), while negative gate voltage reduces the concomitant preferential orbital occupancy and magnetic anisotropy. Besides its fundamental significance in orbital physics, our findings might advance the process towards practical oxide-electronics based on orbital.

cond-mat.mtrl-sci↗

arXiv2012

All-electrical measurements of direct spin Hall effect in GaAs with Esaki diode electrodes

We report on measurements of direct spin Hall effect in a lightly n-doped GaAs channel. As spin detecting contacts we employed highly efficient ferromagnetic Fe/(Ga,Mn)As/GaAs Esaki diode structures. We investigate bias and temperature dependence of the measured spin Hall signal and evaluate the value of total spin Hall conductivity and its dependence on channel conductivity and temperature. From the results we determine skew scattering and side jump contribution to the total spin hall conductivity and compare it with the results of experiments on higher conductive n-GaAs channels[Phys. Rev. Lett. 105,156602(2010)]. As a result we conclude that both skewness and side jump contribution cannot be fully independent on the conductivity of the channel.

cond-mat.mes-hall↗