A5016666318- Magnetic properties of thin films
- Advanced Memory and Neural Computing
- Ferroelectric and Negative Capacitance Devices
- Magnetic and transport properties of perovskites and related materials
- Quantum and electron transport phenomena
- Magnetic Properties and Applications
- ZnO doping and properties
- Physics of Superconductivity and Magnetism
- Multiferroics and related materials
- Magneto-Optical Properties and Applications
- Magnetic Field Sensors Techniques
- Semiconductor materials and devices
- Characterization and Applications of Magnetic Nanoparticles
- Theoretical and Computational Physics
- Energy Harvesting in Wireless Networks
- Magnetic Properties of Alloys
- Neural Networks and Applications
- Electronic and Structural Properties of Oxides
- Metallic Glasses and Amorphous Alloys
- Neural Networks and Reservoir Computing
- Advanced Data Storage Technologies
- Photonic Crystals and Applications
- Advanced Antenna and Metasurface Technologies
- Mechanical and Optical Resonators
- Metamaterials and Metasurfaces Applications
Northwestern University
2018-2025
Golestan University of Medical Sciences
2022
University of California, Los Angeles
2010-2019
Inston (United States)
2014-2018
Fudan University
2016
IBM Research - Thomas J. Watson Research Center
2016
Argonne National Laboratory
2016
Adana Science and Technology University
2016
Islamic Azad University of Kermanshah
2016
Islamic Azad University Kerman
2016
The quest for novel low-dissipation devices is one of the most critical future semiconductor technology and nano-systems. development a low-power, universal memory will enable new paradigm non-volatile computation. Here we consider STT-RAM as emerging candidates low-power memory. We show different configurations STT demonstrate strategies to optimize key performance parameters such switching current energy. energy scaling limits are discussed, leading us argue that alternative writing...
Magnetic skyrmions, which are topologically protected spin textures, promising candidates for ultralow-energy and ultrahigh-density magnetic data storage computing applications. To date, most experiments on skyrmions have been carried out at low temperatures. The choice of available materials is limited, there a lack electrical means to control in devices. In this work, we demonstrate new method creating stable skyrmion bubble phase the CoFeB–MgO material system room temperature, by...
The electronic and optoelectronic properties of two dimensional materials have been extensively explored in graphene layered transition metal dichalcogenides (TMDs). Spintronics these two-dimensional could provide novel opportunities for future electronics, example, efficient generation spin current, which should enable the manipulation magnetic elements. So far, quantitative determination charge current induced spin-orbit torques (SOTs) on layer adjacent to is still lacking. Here, we report...
We demonstrate excitation of ferromagnetic resonance in $\mathrm{CoFeB}/\mathrm{MgO}/\mathrm{CoFeB}$ magnetic tunnel junctions (MTJs) by the combined action voltage-controlled anisotropy (VCMA) and spin transfer torque (ST). Our measurements reveal that GHz-frequency VCMA ST low-resistance MTJs have similar magnitudes, thus both torques are equally important for understanding high-frequency voltage-driven magnetization dynamics MTJs. As an example, we show can increase sensitivity MTJ-based...
Reconfiguring and programming the action of a magnetically driven robot using light.
We report electric-field-induced switching with write energies down to 6 fJ/bit for times of 0.5 ns, in nanoscale perpendicular magnetic tunnel junctions (MTJs) high resistance-area product and diameters 50 nm. The ultra-low energy is made possible by a thick MgO barrier that ensures negligible spin-transfer torque contributions, along reduction the Ohmic dissipation. find voltage time are insensitive junction diameter high-resistance MTJs, result accounted macrospin model purely...
Current-induced spin-orbit torques (SOTs) are of interest for fast and energy-efficient manipulation magnetic order in spintronic devices. To be deterministic, however, switching perpendicularly magnetized materials by SOT requires a mechanism in-plane symmetry breaking. Existing methods to do so involve the application an bias field, or incorporation structural asymmetry device, both which can difficult implement practical applications. Here, we report bias-field-free single perpendicular...
We present in-plane CoFeB–MgO magnetic tunnel junctions with perpendicular anisotropy in the free layer to reduce spin transfer induced switching current. The tunneling magnetoresistance ratio, resistance-area product, and current densities are compared different CoFeB compositions. effects of thickness on its current-induced characteristics studied by vibrating sample magnetometry electrical transport measurements patterned elliptical nanopillar devices. Switching ∼4 MA/cm2 obtained at 10...
The spin-transfer nano-oscillator (STNO) offers the possibility of using transfer spin angular momentum via spin-polarized currents to generate microwave signals. However, at present STNO emission mainly relies on both large drive and external magnetic fields. These issues hinder implementation STNOs for practical applications in terms power dissipation size. Here, we report measurements built with MgO-based tunnel junctions having a planar polarizer perpendicular free layer, where output...
We report giant reversible and permanent magnetic anisotropy reorientation between two perpendicular easy axes in a magnetoelectric polycrystalline Ni thin film (011) oriented [Pb(Mg1/3Nb2/3)O3](1−x)-[PbTiO3]x (PMN-PT) heterostructure. The PMN-PT is partially poled prior to deposition provide remanent strain bias. Following full poling of the sample, strains equal opposite values are used reversibly permanently reorient magnetization state film. These experimental results integrated into...
In this work, we report on the demonstration of voltage-driven spin wave excitation, where waves are generated by multiferroic magnetoelectric (ME) cell transducers driven an alternating voltage, rather than electric current. A element consisting a magnetostrictive Ni film and piezoelectric [Pb(Mg1/3Nb2/3)O3](1−x)–[PbTiO3]x substrate was used for purpose. By applying AC voltage to piezoelectric, oscillating field is created within material, which results in strain-induced magnetic anisotropy...
Microwave detectors based on the spin-transfer torque diode effect are among key emerging spintronic devices. By utilizing spin of electrons in addition to charge, they have potential overcome theoretical performance limits their semiconductor (Schottky) counterparts, which cannot operate at low input power. Here, we demonstrate nanoscale microwave exhibiting record-high detection sensitivity 75400 mV mW$^{-1}$ room temperature, without any external bias fields, for power down 10 nW. This is...
We review the recent progress in development of magnetoelectric RAM (MeRAM) based on electric-field-controlled writing magnetic tunnel junctions (MTJs). MeRAM uses tunneling magnetoresistance effect for readout a two-terminal memory element, similar to other types RAM. However, information is performed by voltage control anisotropy (VCMA) at interface an MgO barrier and CoFeB-based free layer, as opposed current-controlled (e.g., spin-transfer torque or spin-orbit torque) mechanisms. present...
Electric-field-control of magnetism can dramatically improve the energy efficiency spintronic devices and enhance performance magnetic memories. More generally, it expands range applications nonvolatile devices, by making them energetically competitive compared to conventional semiconductor solutions for logic computation, thereby potentially enabling a new generation ultralow-power systems. This paper reviews recent experiments on voltage-controlled anisotropy (VCMA) effect in thin films,...
The excitation of the steady-state precessions magnetization opens a new way for nanoscale microwave oscillators by exploiting transfer spin angular momentum from spin-polarized current to ferromagnet, referred as spin-transfer nano-oscillators (STNOs). For STNOs be practical, however, their relatively low output power and large line width must improved. Here we demonstrate that signals with maximum measured 0.28 μW simultaneously narrow 25 MHz can generated CoFeB-MgO-based magnetic tunnel...
The influence of spin-Hall-effect spin torque (SHE-ST) induced by in-plane charge current was studied in microscale Ta/Co${}_{20}$Fe${}_{60}$B${}_{20}$/TaO${}_{x}$ films with perpendicular magnetization. Simultaneous electrical transport and polar magneto-optical Kerr effect (MOKE) imaging experiments were used to investigate the switching dynamics. A rich set behaviors observed, which can be well understood analyzing a switching-phase diagram MOKE images, considering competition between...
In this work, we experimentally study the temperature dependence of perpendicular magnetic anisotropy (PMA) and voltage-controlled (VCMA) in nanoscale MgO|CoFeB|Ta-based tunnel junctions. We demonstrate that dependences both PMA VCMA coefficient follow power laws saturation magnetization, but with different exponents. also find linear on electric field is maintained over a wide range, although strength decreases faster as function compared to PMA. Possible mechanisms leading exponents are discussed.
This work investigated in-plane MgO-based magnetic tunnel junctions (MTJs) for the application of spin torque transfer random access memory (STT-RAM). The MTJ in this had an resistance area product (RA) = 4.3 Ω·μm2, tunneling magnetoresistance ratio ∼135%, thermal stability factor Δ(H)=68 (by field measurement), and Δ(I) 50 current measurement). optimal writing energy was found to be 0.286 pJ per bit at 1.54 ns antiparallel (AP) state parallel (P) switching, 0.706 0.68 P AP switching. Ultra...
Magnetic skyrmions as swirling spin textures with a nontrivial topology have potential applications magnetic memory and storage devices. Since the initial discovery of in non-centrosymmetric B20 materials, recent effort has focused on exploring room-temperature heavy metal ferromagnetic heterostructures, material platform compatible existing spintronic manufacturing technology. Here, we report surprising observation that skyrmion phase can be stabilized an entirely different class systems...
We studied the impact of different insertion layers (Ta, Pt, and Mg) at CoFeB|MgO interface on voltage-controlled magnetic anisotropy (VCMA) effect other properties. Inserting a very thin Mg layer 0.1–0.3 nm yielded VCMA coefficient 100 fJ/V-m, more than 3 times higher average values around 30 fJ/V-m reported in Ta|CoFeB|MgO-based structures. Ta Pt also showed small improvement, yielding coefficients 40 fJ/V-m. Electrical, magnetic, X-ray diffraction results reveal that 1.2 gives rise to...
We theoretically study equilibrium and dynamic properties of nanosized magnetic skyrmions in thin films with broken inversion symmetry, where electric field couples to magnetization via spin-orbit coupling. Based on a symmetry-based phenomenology micromagnetic simulations we show that this electric-field coupling, renormalizing the energy, modifies skyrmion. This change, turn, results significant alteration current-induced skyrmion motion. Particularly, speed direction can be manipulated by...
We demonstrate strain-induced modulation of perpendicular magnetic anisotropy (PMA) in (001)-oriented [Pb(Mg1/3Nb2/3)O3](1−x)-[PbTiO3]x (PMN-PT) substrate/Ta/CoFeB/MgO/Ta structures using ferromagnetic resonance (FMR). An in-plane biaxial strain is produced by applying voltage between the two surfaces PMN-PT substrate, and transferred to CoFeB layer, which results tuning PMA layer. The change quantitatively extracted from experimental FMR spectra. It shown that both first second-order terms...