Control of magnetism by electric fields

Matsukura, F.; Tokura, Y.; Ohno, Hideo

doi:10.1038/nnano.2015.22

Cited by 854 publications

(605 citation statements)

References 127 publications

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“…For sufficiently high fields (1-10 MV cm -1 ) at THz and mid-infrared frequencies, the tunnelling regime (γ < 1) is operative, resulting in novel phenomena and unexpected effects such as massive population transfer between bands far in excess of the photon energy (that is, E g >> ħω) 44,48,49 . An exciting research direction that will remain outside of the scope of this Review is the electrical and optical control of magnetism 50,51 .…”

Section: Nature Materials Doi: 101038/nmat5017mentioning

confidence: 99%

Towards properties on demand in quantum materials

2017

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Q uantum materials are on the ascent. This term embodies a vast portfolio of compounds and phenomena where ramifications of quantum mechanics are demonstrably real. Quantum materials are in the vanguard of contemporary physics in part because these systems afford an exceptional venue to uncover the many roles of symmetry, topology, dimensionality and strong correlations in macroscopic observables. Here we set out to explore the ways and means of creating new states of matter in quantum materials and manipulating their phases via external stimuli. Practical control of these properties is a precondition for exploiting quantum advantages in new photonic, electronic and energy technologies, a task of significant societal impact 1 . We will primarily focus on the following classes of quantum materials: transition metal oxides, Fe-and Cu-based high-T c superconductors, van der Waals semiconductors, topological insulators and Weyl semimetals, and, finally, graphene.The properties of quantum materials are anomalously sensitive to external stimuli. In these systems, interactions associated with spin, charge, lattice and orbital degrees of freedom are commonly on par with the electronic kinetic energy. A rather fragile balance between coexisting and competing ground states can be readily shifted via external stimuli, leading to a raft of quantum phases and transitions between them 2,3 . Furthermore, certain classes of driven quantum states (Fig. 1a and Box 1) are explicit products of coherent interaction between light and matter 4-6 . Alternatively, the properties of quantum materials can be pre-programmed by directly manipulating the electronic wavefunction and the attendant Berry phase that give rise to the anomalous velocity of electrons in a solid [7][8][9] . These complementary avenues of controls mean that investigations no longer need to be reduced to merely observing (in contrast, for example, to astrophysics). Instead, it is now feasible to attain, in a predictable fashion, 'properties on demand' by steering a quantum material towards a desirable ground, metastable or transient state. The past decade has witnessed an explosion in the field of quantum materials, headlined by the predictions and discoveries of novel Landau-symmetry-broken phases in correlated electron systems, topological phases in systems with strong spin-orbit coupling, and ultra-manipulable materials platforms based on two-dimensional van der Waals crystals. Discovering pathways to experimentally realize quantum phases of matter and exert control over their properties is a central goal of modern condensed-matter physics, which holds promise for a new generation of electronic/photonic devices with currently inaccessible and likely unimaginable functionalities. In this Review, we describe emerging strategies for selectively perturbing microscopic interaction parameters, which can be used to transform materials into a desired quantum state. Particular emphasis will be placed on recent successes to tailor electronic interaction parameters through th...

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Section: Nature Materials Doi: 101038/nmat5017mentioning

confidence: 99%

Towards properties on demand in quantum materials

2017

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“…One of the most important functions related to E-controlled magnetism 45 is the dynamical ME response. The (linear) ME susceptibility α ij can be extended to the a.c. or optical frequency region, such that P i (ω) = α ij (ω)H j (ω) and M i (ω)= t α ij (ω)E j (ω).…”

Section: Reproduced From Ref 39 Iop (A-c); and Ref 42 Macmillan Pmentioning

confidence: 99%

Emergent functions of quantum materials

2017

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Materials can harbour quantum many-body systems, most typically in the form of strongly correlated electrons in solids, that lead to novel and remarkable functions thanks to emergence-collective behaviours that arise from strong interactions among the elements. These include the Mott transition, high-temperature superconductivity, topological superconductivity, colossal magnetoresistance, giant magnetoelectric e ect, and topological insulators. These phenomena will probably be crucial for developing the next-generation quantum technologies that will meet the urgent technological demands for achieving a sustainable and safe society. Dissipationless electronics using topological currents and quantum spins, energy harvesting such as photovoltaics and thermoelectrics, and secure quantum computing and communication are the three major fields of applications working towards this goal. Here, we review the basic principles and the current status of the emergent phenomena and functions in materials from the viewpoint of strong correlation and topology.E mergence is a concept developed for many-body systems, indicating the properties, phenomena, and functions that never appear in the individual elements but are realized only when a huge number of elements get together 1 . Inside materials, emergent phenomena are often seen due to the interaction of electronic states; with recent developments on electronic states in solids schematically summarized in Fig. 1a. Electrons in solids have several degrees of freedom: charge, spin and orbital, and are characterized by the topological nature determined by the atomic potential on the crystal lattice structure, as schematically shown in Fig. 1b. These five attributes are coupled together and determine the overall responses to stimuli, which appear as materials' electrical, magnetic, optical, thermal, and mechanical properties.These collective electrons demonstrate various macroscopic quantum phenomena, the representative example of which is superconductivity. One of the big challenges in condensed matter physics is to increase the temperature (T c ) at which superconductivity can be observed to above room temperature. However, there are many other macroscopic quantum phenomena that are already observable above room temperature. One is magnetism (by the Bohr-van Leeuwen theorem), and the other is ferroelectricity 2,3 . Remarkably, there are common features of these three macroscopic quantum phenomena: the order parameter, which is of quantum origin, behaves as a classical quantity, and the quantum topology plays a crucial role.The topological nature of the electronic states is the key concept in the most recent developments in understanding quantum materials. The quantum Hall effect, topological insulators, and topological superconductors are all characterized by nontrivial topologies in Hilbert space. The Berry phase, which describes the connection and curvature of the subspace of Hilbert space, plays the central role in the unified principle to describe this topological nature 4 . ...

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“…The observed sign was consistent with the conventional VCMA effect observed in Fe-based alloy/MgO junctions. [4][5][6] As the tunneling conductance depends on the relative angle (θ) between two magnetic layers, the ratio of the in-plane component of the magnetization of the ultrathin Ir-doped Fe layer (M in-plane ) to its …”

Section: Highly Efficient Voltage Control T Nozaki Et Almentioning

confidence: 99%

“…Among various approaches to the electric field manipulation of magnetism, 4 the voltage-controlled magnetic anisotropy (VCMA) effect in a 3d transition ultrathin ferromagnetic metal layer has attracted much attention as a promising solution. 5,6 The achievement of the VCMA effect in MgO-based MTJs 7 and the demonstration of high-speed responses, such as voltage-induced ferromagnetic resonance (FMR) excitation, 8,9 spin-wave excitation 10 and dynamic magnetization switching, [11][12][13][14] have brought great changes to research in this field.…”

Section: Introductionmentioning

confidence: 99%

Highly efficient voltage control of spin and enhanced interfacial perpendicular magnetic anisotropy in iridium-doped Fe/MgO magnetic tunnel junctions

et al. 2017

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Voltage control of spin enables both a zero standby power and ultralow active power consumption in spintronic devices, such as magnetoresistive random-access memory devices. A practical approach to achieve voltage control is the electrical modulation of the spin-orbit interaction at the interface between 3d-transition-ferromagnetic-metal and dielectric layers in a magnetic tunnel junction (MTJ). However, we need to initiate a new guideline for materials design to improve both the voltage-controlled magnetic anisotropy (VCMA) and perpendicular magnetic anisotropy (PMA). Here we report that atomic-scale doping of iridium in an ultrathin Fe layer is highly effective to improving these properties in Fe/MgO-based MTJs. A large interfacial PMA energy, K i,0 , of up to 3.7 mJ m − 2 was obtained, which was 1.8 times greater than that of the pure Fe/MgO interface. Moreover, iridium doping yielded a huge VCMA coefficient (up to 320 fJ Vm − 1 ) as well as high-speed response. First-principles calculations revealed that Ir atoms dispersed within the Fe layer play a considerable role in enhancing K i,0 and the VCMA coefficient. These results demonstrate the efficacy of heavy-metal doping in ferromagnetic layers as an advanced approach to develop high-density voltage-driven spintronic devices. NPG Asia Materials (2017) 9, e451; doi:10.1038/am.2017.204; published online 5 December 2017 INTRODUCTIONSpintronic devices, such as a magnetoresistive random-access memory device using a MgO-based magnetic tunnel junction (MTJ), 1,2 are expected to reduce the standby power of future computing systems by utilizing the non-volatile feature of magnetism. However, one significant challenge emerges from reducing the energy for information writing: magnetization switching. This issue is caused by electriccurrent-based operations of spintronic devices using electric-currentinduced magnetic fields, spin-transfer torque (STT) and spin-orbit torque based on the spin Hall effect rather than the electric-field-based operations presently used for semiconductor devices. For example, recent developments of STT-magnetoresistive random access memory have achieved~100 fJ per bit writing energies, 3 which corresponds to 10 7 k B T, where k B is the Boltzmann constant and T is the temperature (assumed to be 300 K here). In contrast, the energy required for maintaining magnetic information, that is, thermal stability, is between 60 k B T and 100 k B T. This large energy gap between data writing and retention, on the order of 10 5 , mainly originates

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Control of magnetism by electric fields

Cited by 854 publications

References 127 publications

Towards properties on demand in quantum materials

Towards properties on demand in quantum materials

Emergent functions of quantum materials

Highly efficient voltage control of spin and enhanced interfacial perpendicular magnetic anisotropy in iridium-doped Fe/MgO magnetic tunnel junctions

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