Spintronics: A Spin-Based Electronics Vision for the Future

Wolf, Stuart A.; Awschalom, D. D.; Buhrman, R. A.; Daughton, J.M.; Molnár, S. von; Roukes, M. L.; Chtchelkanova, Almadena; Treger, Daryl

doi:10.1126/science.1065389

Cited by 10,857 publications

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References 111 publications

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“…Much more efficient devices for low-power data storage and processing could be realized if the spin degree of freedom were used in addition 1,2,3,4 . The spintronics approach requires the generation and control of spin currents, that is, the transport of spin angular momentum through space 5,6 .…”

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confidence: 99%

Terahertz spin current pulses controlled by magnetic heterostructures

et al. 2013

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In spin-based electronics, information is encoded by the spin state of electron bunches 1,2,3,4 . Processing this information requires the controlled transport of spin angular momentum through a solid 5,6 , preferably at frequencies reaching the so far unexplored terahertz (THz) regime 7,8,9 . Here, we demonstrate, by experiment and theory, that the temporal shape of femtosecond spin-current bursts can be manipulated by using specifically designed magnetic heterostructures. A laser pulse is employed to drive spins 10,11,12 from a ferromagnetic Fe thin film into a nonmagnetic cap layer that has either low (Ru) or high (Au) electron mobility. The resulting transient spin current is detected by means of an ultrafast, contactless amperemeter 13 based on the inverse spin Hall effect 14,15 that converts the spin flow into a THz electromagnetic pulse. We find that the Ru cap layer yields a considerably longer spin-current pulse because electrons are injected in Ru d states that have a much smaller mobility than Au sp states 16 . Thus, spin current pulses and the resulting THz transients can be shaped by tailoring magnetic heterostructures, which opens the door for engineering high-speed spintronic devices as well as broadband THz emitters 7,8,9 , in particular covering the elusive range from 5 to 10THz.Contemporary electronics is based on the electron charge as information carrier whose presence or absence encodes the value of a bit. Much more efficient devices for low-power data storage and processing could be realized if the spin degree of freedom were used in addition 1,2,3,4 . The spintronics approach requires the generation and control of spin currents, that is, the transport of spin angular momentum through space 5,6 . Spintronic operations should be performed at a pace exceeding that of today's computers, which ultimately requires the generation of spin current pulses with terahertz (1 THz = 10 12 Hz) bandwidths 7,8 as well as the possibility to manipulate them in novel structures 17,18 . To date, femtosecond spin-current pulses have been successfully launched by optically exciting electrons in semiconductors 10 or ferromagnetic metals 11,12 . However, to enable ultrafast basic operations on these transients (such as buffering or delaying), their shape and propagation have to be controlled on subpicosecond time scales.Here, we employ magnetic heterostructures containing an optimally chosen nonmagnetic metallic layer whose electron mobility allows us either to trap or to transmit electrons and, thus, to engineer ultrafast spin pulses. The spin flow is probed in a contactless manner using the inverse spin Hall effect 14,15 (ISHE) that converts the spin current into a detectable THz electromagnetic pulse 13 . Our findings open up a route to device-oriented femtosecond spintronics as well as novel broadband emitters of THz radiation 7,8,9 .Our idea is illustrated in Fig. 1a, which shows a schematic of a ferromagnetic Fe film capped by a thin layer of Ru or Au. Absorption of a femtosecond laser pulse (photon energy 1...

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Terahertz spin current pulses controlled by magnetic heterostructures

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“…PACS numbers: 71.20.Rv, 75.75.+a, 82.35.Lr It is expected that the new generation of devices will exploit spin dependent effects, what has been called spintronics [1,2]. A challenge now facing spintronics is transmitting spin signals over long enough distances to allow for spin manipulation.…”

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“…We suggest that the hexagonal bundles composed by these polymers might display intrachain ferromagnetic order at finite temperature by introducing interchain exchange coupling. It is expected that the new generation of devices will exploit spin dependent effects, what has been called spintronics [1,2]. A challenge now facing spintronics is transmitting spin signals over long enough distances to allow for spin manipulation.…”

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“…The former sandwich structure is characteristic of the complexes for early transition metals (Sc-V), whereas the latter is formed for late transition metals (Fe-Ni). Cr(Bz) 2 and Mn(Bz) 2 with a sandwich structure are also observed experimentally [12]. Although the multidecker sandwich M n (Bz) m clusters have been extensively studied theoretically [13,14,15,16], however, studies of the 1D [TM(Bz)] ∞ polymers are still very lacking.…”

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One-Dimensional Transition Metal−Benzene Sandwich Polymers: Possible Ideal Conductors for Spin Transport

et al. 2006

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We investigate the electronic and magnetic properties of the proposed one-dimensional transition metal (TM=Sc, Ti, V, Cr, and Mn) -benzene (Bz) sandwich polymers by means of density functional calculations. [V(Bz)]∞ is found to be a quasi-half-metallic ferromagnet and half-metallic ferromagnetism is predicted for [Mn(Bz)]∞. Moreover, we show that stretching the [TM(Bz)]∞ polymers could have dramatic effects on their electronic and magnetic properties. The elongated [V(Bz)]∞ displays half-metallic behavior, and [Mn(Bz)]∞ stretched to a certain degree becomes an antiferromagnetic insulator. The possibilities to stabilize the ferromagnetic order in [V(Bz)]∞ and [Mn(Bz)]∞ polymers at finite temperature are discussed. We suggest that the hexagonal bundles composed by these polymers might display intrachain ferromagnetic order at finite temperature by introducing interchain exchange coupling.PACS numbers: 71.20.Rv, 75.75.+a, 82.35.Lr It is expected that the new generation of devices will exploit spin dependent effects, what has been called spintronics [1,2]. A challenge now facing spintronics is transmitting spin signals over long enough distances to allow for spin manipulation. An ideal device for spin-polarized transport should have several key ingredients. First, it should work well at room temperature and should offer as high a magnetoresistance (MR) ratio as possible. In this sense, a half-metallic (HM) ferromagnet with the Curie temperature higher than room temperature is highly desirable since there would be only one electronic spin channel at the Fermi energy [3]. Second, the size or diameter of the materials should be uniform for large scale applications. Carbon nanotubes (CNTs) were considered as promising one-dimensional (1D) spin mediators because of their ballistic nature of conduction and relatively long spin scattering length (at least 130 nm) [4,5]. Coherent spin transport has been observed in multiwalled CNT systems with Co electrodes. The maximum MR ratio of 9% was observed in multiwalled CNTs at 4.2 K. However, as the temperature increases to 20 K, the MR ratio goes to zero, preventing any room temperature applications [4]. A theoretical work suggested that the ferromagnetic (FM) transition-metal (TM) /CNT hybrid structures may be used as devices for spin-polarized transport to further increase the MR ratio [6]. Unfortunately, although large spin polarization is found in these systems, there is no HM behavior. Another difficulty with CNT is that the devices are unlikely to be very reproducible due to the wide assortment of tube size and helicity that is produced during synthesis. Wide variation in device behavior was reported in the CNT experiment [4].Recently, an experimental study suggested that the unpaired electrons on the metal atoms couple ferromagnetically in the multidecker organometallic sandwich Vbenzene (Bz) complexes, i.e., V n (Bz) n+1 clusters [7]. The FM sandwich clusters are supposed to serve as nanomagnetic building blocks in applications such as recording media or spintronic de...

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“…Strong correlation of spin and charge degrees of freedom in the same material makes it possible to manipulate magnetically stored information with electric fields and/or modify fast logic gates by changing the magnetisation of their components. In metal multilayers, such effects are manifest in giant magnetoresistance, where the orientations of the macroscopic magnetisation in adjacent layers determine the electrical resistance of the structure [1,2]. Metallic spintronic devices, such as hard disk read heads and magnetic random access memory are among the most successful technologies of the past decades.…”

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Direct Epitaxial Integration of the Ferromagnetic Semiconductor EuO with Silicon for Spintronic Applications

Averyanov

Sadofyev

Tokmachev

et al. 2015

ACS Appl. Mater. Interfaces

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Materials in which charge and spin degrees of freedom interact strongly offer applications known as spintronics. Following a remarkable success of metallic spintronics based on the giant-magnetoresistive effect, tremendous efforts have been invested into the less developed semiconductor spintronics, in particular, with the aim to produce three-terminal spintronic devices, e.g. spin transistors. One of the most important prerequisites for such a technology is an effective injection of spin-polarized carriers from a ferromagnetic semiconductor into a nonmagnetic semiconductor, preferably one of those currently used for industrial applications such as Si -a workhorse of modern electronics. Ferromagnetic semiconductor EuO is long believed to be the best candidate for integration of magnetic semiconductor with Si. Although EuO proved to offer optimal conditions for effective spin injection into silicon and in spite of considerable efforts, the direct epitaxial stabilization of stoichiometric EuO thin films on Si without any buffer layer has not been demonstrated to date. Here we report a new technique for control of EuO/Si interface on submonolayer level which may have general implications for the growth of functional oxides on Si. Using this technique we solve a long-standing problem of direct epitaxial growth on silicon of thin EuO films which exhibit structural and magnetic properties of EuO bulk material. This result opens up new possibilities in developing all-semiconductor spintronic devices.Modern information technology is based on the fundamental dichotomy: it utilizes charge of electrons to process information in semiconductors and their spin to store information in magnetic materials. Strong correlation of spin and charge degrees of freedom in the same material makes it possible to manipulate magnetically stored information with electric fields and/or modify fast logic gates by changing the magnetisation of their components. In metal multilayers, such effects are manifest in giant magnetoresistance, where the orientations of the macroscopic magnetisation in adjacent layers determine the electrical resistance of the structure [1,2]. Metallic spintronic devices, such as hard disk read heads and magnetic random access memory are among the most successful technologies of the past decades. However, metals cannot enhance signals -the prerequisite for transistor technology readily offered by semiconductors.The development of semiconductor spintronics requires the ability to inject, modulate and detect spin-polarized carriers in a single device, preferably made of technologically important materials currently used in integrated circuits such as Si or GaAs [3,4]. Thus far, the spin of the carriers has played a minor role in semiconductor devices mainly because Si and GaAs are nonmagnetic. On the other hand, the enhanced spin-related phenomena realized in diluted magnetic semiconductors (DMS) (especially 2 GaMnAs films [5]) open the way for applications in spintronics [6]. The interplay between electrical and magneti...

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Spintronics: A Spin-Based Electronics Vision for the Future

Cited by 10,857 publications

References 111 publications

Terahertz spin current pulses controlled by magnetic heterostructures

Terahertz spin current pulses controlled by magnetic heterostructures

One-Dimensional Transition Metal−Benzene Sandwich Polymers: Possible Ideal Conductors for Spin Transport

Direct Epitaxial Integration of the Ferromagnetic Semiconductor EuO with Silicon for Spintronic Applications

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