Spintronics, a transformative field of research, leverages the spin of electron to revolutionize electronic devices, offering significant advantages over traditional charge-based systems. This chapter highlights the critical role of novel magnetic materials in advancing spintronic technologies by addressing their fundamental properties, fabrication methods, and applications. A diverse range of materials, including ferromagnetic, antiferromagnetic, non-collinear antiferromagnetic, synthetic antiferromagnetic, ferrimagnetic, and multiferroic systems, is explored for their unique contributions to spintronic devices. Advanced fabrication techniques, such as bulk crystal formation, thin-film deposition, and nano-structuring, are detailed along characterization methods including spin-orbit torque analysis and magnetization dynamics studies. Emerging research on three-dimensional spin textures, domain walls, skyrmions, and magnons highlighted for its potential for novel spintronic applications. Additionally, the chapter reviews applications in memory technologies, spintronic nano-oscillators, and neuromorphic computing. Finally, it concludes by examining future research directions, challenges, and opportunities in spintronics, providing insights into breakthroughs that are shaping the future of this rapidly evolving field.
We investigate spin precession (Hanle effect) in the prototypical organic spintronic giant magnetoresistance (GMR) device La0.7Sr0.3MnO3(LSMO)/tris(8-hydroxyquinoline)(Alq3)/AlOx/Co. The Hanle effect is not observed in measurements taken by sweeping a magnetic field at different angles from the plane of the device. As possible explanations we discuss the tilting out of plane of the magnetization of the electrodes, exceptionally high mobility or hot spots. Our results call for a greater understanding of spin injection and transport in such devices.
By using first-principles calculations, we predict that an in-plane homogenous electrical field can induce half-metallicity in hydrogen-terminated zigzag silicene and germanene nanoribbons (ZSiNRs and ZGeNRs). A dual-gated finite ZSiNR device reveals a nearly perfect spin-filter efficiency of up to 99% while a quadruple-gated finite ZSiNR device serves as an effective spin field effect transistor (FET) with an on/off current ratio of over 100 from ab initio quantum transport simulation. This discovery opens up novel prospect of silicene and germanene in spintronics.
In recent years, the field of antiferromagnetic spintronics has been substantially advanced. Electric-field control is a promising approach to achieving ultra-low power spintronic devices via suppressing Joule heating. In this article, cutting-edge research, including electric-field modulation of antiferromagnetic spintronic devices using strain, ionic liquids, dielectric materials, and electrochemical ionic migration, are comprehensively reviewed. Various emergent topics such as the Neel spin-orbit torque, chiral spintronics, topological antiferromagnetic spintronics, anisotropic magnetoresis…
This paper reports our Monte Carlo (MC) studies aiming to explain the experimentally observed paramagnetic molecule induced antiferromagnetic coupling between the ferromagnetic (FM) electrodes. Recently developed magnetic tunnel junction based molecular spintronics devices (MTJMSDs), which were prepared by chemically bonding the paramagnetic molecules between the FM electrodes along the exposed side edges of magnetic tunnel junctions, exhibited molecule induced strong antiferromagnetic coupling. Our MC studies focused on the atomic model analogous to the MTJMSD and studied the effect of molecu…
We present cmtj - a comprehensive simulation package that allows large-scale macrospin simulations for a variety of multilayer spintronics devices. Apart from conventional static simulations, such as magnetoresistance and magnetisation hysteresis loops, cmtj implements a mathematical model of dynamic experimental techniques commonly used for spintronics devices characterisation, for instance: spin diode ferromagnetic resonance, pulse-induced microwave magnetometry, or harmonic Hall voltage measurements. We demonstrate the accuracy of the macrospin simulations on a variety of examples, accompan…
We have fabricated graphene spin-valve devices utilizing scalable materials made from chemical vapor deposition (CVD). Both the spin-transporting graphene and the tunnel barrier material are CVD-grown. The tunnel barrier is realized by h-BN, used either as a monolayer or bilayer and placed over the graphene. Spin transport experiments were performed using ferromagnetic contacts deposited onto the barrier. We find that spin injection is still greatly suppressed in devices with a monolayer tunneling barrier due to resistance mismatch. This is, however, not the case for devices with bilayer barri…
The isolation of graphene has triggered an avalanche of studies into the spin-dependent physical properties of this material, as well as graphene-based spintronic devices. Here we review the experimental and theoretical state-of-art concerning spin injection and transport, defect-induced magnetic moments, spin-orbit coupling and spin relaxation in graphene. Future research in graphene spintronics will need to address the development of applications such as spin transistors and spin logic devices, as well as exotic physical properties including topological states and proximity-induced phenomena…
The research landscape of magnetism has been recently enriched by the discovery of altermagnetism. It is an unconventional phase of matter characterized by a d-wave (or higher even-parity-wave) collinear compensated spin ordering, which enables strongly spin-polarized currents in the absence of magnetization, and features fast spin dynamics. Simultaneously, on the applied magnetism front, spintronic memories based on conventional ferromagnets are currently turning from a niche to a mass produced integrated-circuit technology as they start to complement semiconductors on advanced-node microproc…
Nanometric magnonic and spintronic devices need magnetic field control in addition to conventional electronic control. In this work we review ways to replace magnetic field control by an electronic one in order to circumvent appearance of stray magnetic fields or the difficulty of creating large magnetic fields over nanometric distances. Voltage control is compared to current control and corresponding devices are compared from their energetic efficiency point of view.
A new magnetic logic overcomes the major limitations of field programmable gate arrays while having a 50% smaller unit cell than conventional designs utilizing magnetic tunnel junctions with one Heusler alloy electrode. These show positive and negative TMR values at different bias voltages at room temperature which generally adds an additional degree of freedom to all spintronic devices.
The conductivity of the system magnetic dielectric (EuO) - graphene channel - ferroelectric substrate was considered. The magnetic dielectric locally transforms the band spectrum of graphene by inducing an energy gap in it and making it spin-asymmetric with respect to the free electrons. The range of spontaneous polarization (2- 5)mC/m2 that can be easily realized in thin films of proper and incipient ferroelectrics, was under examination. It was demonstrated, that if the Fermi level in the graphene channel belongs to energy intervals where the graphene band spectrum, modified by EuO, becomes …
Antiferromagnetic spintronics is an emerging research field whose focus is on the electrical and optical control of the antiferromagnetic order parameter and its utility in information technology devices. An example of recently discovered new concepts is the Néel spin-orbit torque which allows for the antiferromagnetic order parameter to be controlled by an electrical current in common microelectronic circuits. In this review we discuss the utility of antiferromagnets as active and supporting materials for spintronics, the interplay of antiferromagnetic spintronics with other modern research f…
For the last years spin effects in semiconductors have been of great interest not only in the context of solid state physics, but also for their potential usage in technology. In this paper we give a short review of spintronic materials, in which electron spin as an additional degree of freedom is exploited. Afterwards, we discuss the properties of classic, non-magnetic semiconductors, where the efforts are put on enriching the traditional semiconductor technology engaging the electrical effects of spin effects. Various phenomena and scientific state of the art is highlighted.
Dream of developing molecule-based logic and memory device is more than 70-year-old. Presently, molecule-based devices are also considered for quantum computation hardware. The recent studies have shown the molecule connected to metal leads can perform the qubit-based logic operation. This is an interesting question of why experimental progress is still very slow even when the scope of molecule-based devices may govern the advancement of next-generation logic and memory devices for the highest possible computer technologies. Molecules have the potential to be unmatched device elements as chemi…
We investigate the spin transport through strongly anisotropic noncollinear magnetic molecules and find that the noncollinear magnetization acts as a spin-switching device for the current. Moreover, spin currents are shown to offer a viable route to selectively prepare the molecular device in one of two degenerate noncollinear magnetic states. Spin-currents can be also used to create a non-zero density of toroidal magnetization in a recently characterized Dy_3 noncollinear magnet.
Low-cost spintronic devices functioning in zero applied magnetic field are required for bringing the idea of spin-based electronics into the real-world industrial applications. Here we present first microwave measurements performed on nanomagnet devices fabricated by electrodeposition inside porous membranes. In the paper, we discuss in details a microwave resonator consisting of three nanomagnets, which functions in zero external magnetic field. By applying a microwave signal at a particular frequency, the magnetization of the middle nanomagnet experiences the ferromagnetic resonance (FMR), a…
Using first-principles calculations, we explore the possibility of functionalized graphene as high performance two-dimensional spintronics device. Graphene functionalized with O on one side and H on the other side in the chair conformation is found to be a ferromagnetic metal with a spin-filter efficiency up to 85% at finite bias. The ground state of graphene semi-functionalized with F in the chair conformation is an antiferromagnetic semiconductor, and we construct a magnetoresistive device from it by introducing a magnetic field to stabilize its ferromagnetic metallic state. The resulting ro…
Because of its fascinating electronic properties, graphene is expected to produce breakthroughs in many areas of nanoelectronics. For spintronics, its key advantage is the expected long spin lifetime, combined with its large electron velocity. In this article, we review recent theoretical and experimental results showing that graphene could be the long-awaited platform for spintronics. A critical parameter for both characterization and devices is the resistance of the contact between the electrodes and the graphene, which must be large enough to prevent quenching of the induced spin polarizati…
Recent fabrication of atomic precision nanodevices for spintronics greatly boosted their performance and also revealed new interesting features, as oscillating magnetoresistance with number of atomic layers in a multilayered structure. This motivates the need to go beyond the usual theoretical approach of semi-classical continuous layers. Here the simple tight-binding dynamics is used to describe quantum conduction in a multicomponent system with spin-polarized electrodes separated by an ultrathin and atomically coherent non-magnetic spacer (either metallic or insulating). A possibility is ind…
Spintronics involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. The fascinating spin-resolved properties of graphene motivate numerous researchers into the studies of spintronics in graphene and other two-dimensional (2D) materials. Silicene, silicon analog of graphene, is considered as a promising material for spintronics. Here, we present a review on the theoretical advances about the spin-dependent properties including the electric field and exchange field tunable topological properties of silicene and the corresponding spintronic device …
Ferromagnetic electrodes chemically bonded with thiol functionalized molecules can produce novel molecular spintronics devices. However, major challenges lie in developing Ferromagnetic electrodes based commercially viable device fabrication scheme that consider the susceptibility of ferromagnetic electrodes to oxidation, chemical etching, and stress induced deformations during fabrication and usage. This paper studies NiFe, an alloy used in the present day memory devices and high-temperature engineering applications, as a candidate FM electrode for the fabrication of MSDs. Our spectroscopic r…
A spin transport model is employed to study the effects of spin dephasing induced by diffusion-driven transit-time uncertainty through semiconductor spintronic devices where drift is the dominant transport mechanism. It is found that in the ohmic regime, dephasing is independent of transit length, and determined primarily by voltage drop across the spin transport region. The effects of voltage and temperature predicted by the model are compared to experimental results from a 350-micron-thick silicon spin-transport device using derived mathematical expressions of spin dephasing.
We examine the possibility of using graphene nanoribbons (GNRs) with directly substituted chromium atoms as spintronic device. Using density functional theory, we simulate a voltage bias across a constructed GNR in a device setup, where a magnetic dimer has been substituted into the lattice. Through this first principles approach, we calculate the electronic and magnetic properties as a function of Hubbard U, voltage, and magnetic configuration. By calculating of the total energy of each magnetic configuration, we determine that initial antiferromagnetic ground state flips to a ferromagnetic s…
Lateral heterostructures of two-dimensional (2D) materials, integrating different phases or materials into a single piece of nanosheet, have attracted intensive research interests in the past few years for high-performance electronic and optoelectronic devices. It also holds promises to significantly improve the performance and enable new functions of spintronic devices. It is imperative to have a 2D material possessing diverse electronic and magnetic properties that are required in spintronics. In this work, using density functional theory calculations, we surveyed all IV, V and VI group tran…
The Technical Committee of the IEEE Magnetics Society has selected 7 research topics to develop their roadmaps, where major developments should be listed alongside expected timelines; (i) hard disk drives, (ii) magnetic random access memories, (iii) domain-wall devices, (iv) permanent magnets, (v) sensors and actuators, (vi) magnetic materials and (vii) organic devices. Among them, magnetic materials for spintronic devices have been surveyed as the first exercise. In this roadmap exercise, we have targeted magnetic tunnel and spin-valve junctions as spintronic devices. These can be used for ex…
The electronic properties of lanthanide (from Eu to Tm) impurities in wurtzite gallium nitride and zinc oxide were investigated by first principles calculations, using an all electron methodology plus a Hubbard potential correction. The results indicated that the 4f-related energy levels remain outside the bandgap in both materials, in good agreement with a recent phenomenological model, based on experimental data. Additionally, zinc oxide doped with lanthanide impurities became an n-type material, showing a coupling between the 4f-related spin polarized states and the carriers. This coupling …
We have explored the effects of the Li intercalation on the electronic and magnetic properties of transition-metal (TM) doped anatase TiO$_2$. By Li intercalation, Mn-doped TiO$_2$ exhibits the insulator to metal transition. On the other hand, Li-intercalated Fe-doped TiO$_2$ has the insulating ground state for low concentration of Li/Ti=0.067, but the metallic ground state for high concentration of Li/Ti=0.133. We discuss the $n$-type carrier induced ferromagnetism in Li-intercalated TM-doped anatase TiO$_2$. Based on the Li-intercalated TM-doped anatase TiO$_2$, we propose a potential spintr…
We report on graphene-passivated ferromagnetic electrodes (GPFE) for spin devices. GPFE are shown to act as spin-polarized oxidation-resistant electrodes. The direct coating of nickel with few layer graphene through a readily scalable chemical vapour deposition (CVD) process allows the preservation of an unoxidized nickel surface upon air exposure. Fabrication and measurement of complete reference tunneling spin valve structures demonstrates that the GPFE is maintained as a spin polarizer and also that the presence of the graphene coating leads to a specific sign reversal of the magneto-resist…
Doping of the graphene lattice with transition metal atoms resulting in high magnetic anisotropy energy (MAE) is an important goal of materials research owing to its potential application in spintronics. In this article, by using spin-polarized density functional theory including spin-orbit coupling, we examined magnetic properties of graphene with vacancy defects, both bare and nitrogen-decorated, and doped by Cr, Mn and Fe transition metal single atom (TM-SA) and two different TM atoms simultaneously. [...] The computational findings are supplemented by an atomic-resolution characterization …
Control of magnetism without using magnetic fields enables large-scale integration of spintronic devices for memory, computation and communication in the beyond-CMOS era. Mechanisms including spin torque transfer, spin Hall effect, and electric field or strain assisted switching have been implemented to switch magnetization in various spintronic devices. Their operation speed, however, is fundamentally limited by the spin precession time to be longer than 10-100 picoseconds. Overcoming such a speed constraint is critical for the prospective development of spintronics. Here we report the demons…
Perpendicular magnetic tunnel junctions are one of the building blocks for spintronic memories, which allow fast nonvolatile data access, offering substantial potentials to revolutionize the mainstream computing architecture. However, conventional switching mechanisms of such devices are fundamentally hindered by spin polarized currents4, either spin transfer torque or spin orbit torque with spin precession time limitation and excessive power dissipation. These physical constraints significantly stimulate the advancement of modern spintronics. Here, we report an optomagnetic tunnel junction us…
Research in spintronics often involves generation of heat in nanoscale magnetic systems. This heat generation can be intentional, as when studying effects created by an external applied temperature difference, or unintentional, coming as a consequence of driving relatively large charge currents through tiny structures. Understanding and controlling these thermal gradients can present challenges to experimentalists, which are related at some level to the fact that heat flow is much more difficult to isolate and manipulate than charge flow. This paper aims to provide a simple, intuitive framewor…
Molecular bridges covalently bonded to two ferromagnetic electrodes can transform ferromagnetic materials and produce intriguing spin transport characteristics. This paper discusses the impact of molecule induced strong coupling on spin transport. To study the molecular coupling effect organometallic molecular complex (OMC) was bridged between two ferromagnetic electrodes of a magnetic tunnel junction (Ta/Co/NiFe/AlOx/NiFe/Ta) along the exposed side edges. OMCs induced strong iter-ferromagnetic electrode coupling to yield drastic changes in transport properties of the magnetic tunnel junction …
Oxygen-induced Fe surface segregation at the $L1_0$-FePd(001)/graphene heterointerface for spintronics devices: a first-principles study
Kobe University（神户大学）；ENS Paris-Saclay（巴黎萨克雷高等师范学院）；The University of Tokyo（东京大学）；National Institute of Advanced Industrial Science and Technology (AIST)（产业技术综合研究所）；Nagoya University（名古屋大学）
Multiferroic composite materials, consisting of coupled ferromagnetic and piezoelectric phases, are of great importance in the drive towards creating faster, smaller and more energy efficient devices for information and communications technologies. Such devices require thin ferromagnetic films with large magnetostriction and narrow microwave resonance linewidths. Both properties are often degraded, compared to bulk materials, due to structural imperfections and interface effects in the thin films. We report the development of single crystal thin films of Galfenol (Fe81Ga19) with magnetostricti…
Development of future sensor, memory, and computing nanodevices based on novel physical concepts is one of the significant research endeavors in solid-state research. The field of spintronics is one such promising area of nanoelectronics which utilizes both the charge and spin of an electron for device operations. The advantage offered by spin systems is in their non-volatility and low-power functionality. This paper reviews emerging spintronic phenomena and the research advancements in diverse spin based applications. Spin devices and systems for logic, memories, emerging computing schemes, f…
GaAs surface is characterized by a high density of surface states, which preclude the utilization of this semiconducting material for the realization of several advanced devices. Sulfur-based passivation has been found significantly useful in reducing the effect of dangling bonds. In this article first, the problem associated with GaAs surface has been discussed in a tutorial form. Secondly, a brief introduction of a wide variety of surface passivation methods was introduced. Sulfur passivation, the most effective surface state quenching method, has been elaborated. Thirdly, current trends in …
The development of selective high precision chemical functionalization strategies for device fabrication, in conjunction with associated techniques for patterning graphene wafers with atomic accuracy would provide the necessary basis for a post-CMOS manufacturing technology. This requires a thorough understanding of the principles governing the reactivity and patterning of graphene at the sub-nanometer length scale. This article reviews our quest to delineate the principles of graphene chemistry - that is, the chemistry at the Dirac point and beyond, and the effect of covalent chemistry on the…
This letter introduces a micromagnetic model able to characterize the magnetization dynamics in three terminal magnetic tunnel junctions, where the effects of spin-transfer torque and spin-orbit torque are taken into account. Our results predict that the possibility to separate electrically those two torque sources is very promising from a technological point of view for both next generation of nanoscale spintronic oscillators and microwave detectors. A scalable synchronization scheme based on the parallel connection of those three terminal devices is also proposed.
Spintronics aims to utilize the spin degree of freedom for energy-efficient, non-volatile memory and logic devices. In this research update, we review state-of-the-art developments and new directions in charge- and spin-based memory/logic with a focus on spintronics and the fascinating potential for superconductivity to boost spin transmission via spin-polarized quasiparticles or triplet Cooper pairs.
Spin transistors based on a semiconducting channel attached to ferromagnetic electrodes suffer from fast spin decay and extremely low spin injection/detection efficiencies. Here, we propose an alternative all-in-one spin device whose operation principle relies on electric manipulation of the spin lifetime in two-dimensional (2D) SnTe, in which the sizable spin Hall effect eliminates the need for using ferromagnets. In particular, we explore the persistent spin texture (PST) intrinsically present in the ferroelectric phase which protects the spin from decoherence and supports extraordinarily lo…
This focused issue attempts to provide a comprehensive introduction into the field of antiferromagnetic spintronics. Apart from the brief overview below, it features five review articles. The intention is to cover in a coherent and complementary way key physical aspects of the antiferromagnetic spintronics research. These range from microelectronic memory devices and optical manipulation and detection of antiferromagnetic spins, to the fundamentals of antiferromagnetic dynamics in uniform or spin-textured systems, and to the interplay of antiferromagnetic spintronics with topological phenomena…
Although the development of spintronic devices has advanced significantly over the past decade with the use of ferromagnetic materials, the extensive implementation of such devices has been limited by the notable drawbacks of these materials. Antiferromagnets claim to resolve many of these shortcomings leading to faster, smaller, more energy-efficient, and more robust electronics. Antiferromagnets exhibit many desirable properties including zero net magnetization, imperviousness to external magnetic fields, intrinsic high-frequency dynamics with a characteristic precession frequency on the ord…
The electronic structure of the interface between Tris (8-hydroxyquinolino)-aluminum (Alq3) and La0.7Sr0.3MnO3 manganite (LSMO) was investigated by means of photoelectron spectroscopy. As demonstrated recently this interface is characterized by efficient spin injection in organic spintronic devices. We detected a strong interface dipole of about 0.9 eV that shifts down the whole energy diagram of the Alq3 with respect to the vacuum level. This modifies the height of the barriers for the holes injection to 1.7 eV, indicating that hole injection from LSMO into Alq3 is more difficult than it was …
Advancement of molecular devices will critically depend on the approach to establish electrical connections to the functional molecule(s). We produced a molecular device strategy which is based on chemically attaching of molecules between the two magnetic/nonmagnetic metallic electrodes along the multilayer edge(s) of a prefabricated tunnel junction. Here, we present the fabrication methodology for producing these multilayer edge molecular electronics/spintronics devices (MEMEDs/MEMSDs) and details of the associated challenges and their solutions. The key highlight of our MEMED/MEMSD approach …
Spintronic devices, such as non-volatile magnetic random access memories and logic devices, have attracted considerable attention as potential candidates for future high efficient data storage and computing technology. In a heavy metal or other emerging material with strong spin-orbit coupling (SOC), the charge currents induce spin currents or spin accumulations via SOC. The generated spin currents can exert spin-orbit torques (SOTs) on an adjacent ferromagnet, which opens up a new way to realize magnetization dynamics and switching of the ferromagnetic layer for spintronic devices. In the SOT…
The family of organometal trihalide perovskite (OTP), CH3NH3PbX3 (where X is halogen) has recently revolutionized the photovoltaics field and shows promise in a variety of optoelectronic applications. The characteristic spin properties of charge and neutral excitations in OTPs are influenced by the large spin-orbit coupling of the Pb atoms, which may lead to spin-based device applications. Here we report the first studies of pure spin-current and spin-aligned carrier injection in OTP spintronics devices using spin-pumping and spin-injection, respectively. We measure a relatively large inverse-…
Using an electric field instead of an electric current (or a magnetic field) to tailor the electronic properties of magnetic materials is promising for realizing ultralow energy-consuming memory devices because of the suppression of Joule heating, especially when the devices are scaled to the nanoscale. In the review, we summarize recent results on the giant magnetization and resistivity modulation in a metamagnetic intermetallic alloy - FeRh, which is achieved by electric-field-controlled magnetic phase transitions in multiferroic heterostructures. Furthermore, the approach is extended to top…
We report on the first integration of an antiferromagnetic Heusler compound acting as a pinning layer into magnetic tunneling junctions. The antiferromagnet Ru$_2$MnGe is used to pin the magnetization direction of a ferromagnetic Fe layer in MgO based thin film tunnelling magnetoresistance stacks. The samples were prepared using magnetron co-sputtering. We investigate the structural properties by X-ray diffraction and reflection, as well as atomic force and high-resolution transmission electron microscopy. We find an excellent crystal growth quality with low interface roughnesses of 1-3 Å, whi…
Spintronics is the ability of injecting, manipulating and detecting electron spins into solid state systems. Molecular-electronics investigates the possibility of making electronic devices using organic molecules. Traditionally these two burgeoning areas have lived separate lives, but recently a growing number of experiments have indicated a possible pathway towards their integration. This is the playground for molecular-spintronics, where spin-polarized currents are carried through molecules, and in turn they can affect the state of the molecule. We review the most recent advances in molecula…
