The authors show that the magnetization of a magnetostrictive/piezoelectric multiferroic single-domain shapeanisotropic nanomagnet can be switched with very small voltages that generate strain in the magnetostrictive layer. This can be the basis of ultralow power computing and signal processing. With appropriate material choice, the energy dissipated per switching event can be reduced to ∼45 kT at room temperature for a switching delay of ∼100 ns and ∼70 kT for a switching delay of ∼10 ns, if the energy barrier separating the two stable magnetization directions is ∼32 kT . Such devices can be powered by harvesting energy exclusively from the environment without the need for a battery.
A unique combination of low hysteresis, moderate magnetostriction at low magnetic fields, good tensile strength, machinability and recent progress in commercially viable methods of processing iron-gallium alloys make them well poised for actuator and sensing applications. This review starts with a brief historical note on the early developments of magnetostrictive materials and moves to the recent work on FeGa alloys and their useful properties. This is followed by sections addressing the challenges specific to the characterization and processing of FeGa alloys and the state of the art in modeling their actuation and sensing behavior.
Electrically controlled magnetization switching in a multiferroic heterostructure Appl. Phys. Lett. 97, 052502 (2010); 10.1063/1.3475417Effect of thermal fluctuations on switching field of deep submicron sized soft magnetic thin film Switching the magnetization of a shape-anisotropic 2-phase multiferroic nanomagnet with voltage-generated stress is known to dissipate very little energy (<1 aJ for a switching time of $0.5 ns) at 0 K temperature. Here, we show by solving the stochastic Landau-Lifshitz-Gilbert equation that switching can be carried out with $100% probability in less than 1 ns while dissipating less than 1.5 aJ at room temperature. This makes nanomagnetic logic and memory systems, predicated on stress-induced magnetic reversal, one of the most energy-efficient computing hardware extant. We also study the dependence of energy dissipation, switching delay, and the critical stress needed to switch, on the rate at which stress on the nanomagnet is ramped up or down.
A binary switch is the basic building block for information processing. The potential energy profile of a bistable binary switch is a ‘symmetric' double well. The traditional method of switching it from one state (one well) to the other is to tilt the profile towards the desired state. Here, we present a case, where no such tilting is necessary to switch successfully, even in the presence of thermal noise. This happens because of the built-in dynamics inside the switch itself. It differs from the general perception on binary switching that in a ‘symmetric' potential landscape, the switching probability is 50% in the presence of thermal noise. Our results, considering the complete three-dimensional potential landscape, demonstrate intriguing phenomena on binary switching mechanism. With experimentally feasible parameters, we theoretically demonstrate such intriguing possibility in electric field induced magnetization switching of a shape-anisotropic single-domain magnetostrictive nanomagnet with two stable states at room-temperature.
The authors show that it is possible to rotate the magnetization of a multiferroic (strain-coupled two-layer magnetostrictive-piezoelectric) nanomagnet by a large angle with a small electrostatic potential. This can implement Bennett clocking in nanomagnetic logic arrays resulting in unidirectional propagation of logic bits from one stage to another. This method of Bennett clocking is superior to using spin-transfer torque or local magnetic fields for magnetization rotation. For realistic parameters, it is shown that a potential of ~ 0.2 V applied to a multiferroic nanomagnet can rotate its magnetization by nearly 90 0 to implement Bennett clocking.
Nanomagnetic implementations of Boolean logic have attracted attention because of their nonvolatility and the potential for unprecedented overall energy-efficiency. Unfortunately, the large dissipative losses that occur when nanomagnets are switched with a magnetic field or spin-transfer-torque severely compromise the energy-efficiency. Recently, there have been experimental reports of utilizing the Spin Hall effect for switching magnets, and theoretical proposals for strain induced switching of single-domain magnetostrictive nanomagnets, that might reduce the dissipative losses significantly. Here, we experimentally demonstrate, for the first time that strain-induced switching of single-domain magnetostrictive nanomagnets of lateral dimensions ∼200 nm fabricated on a piezoelectric substrate can implement a nanomagnetic Boolean NOT gate and steer bit information unidirectionally in dipole-coupled nanomagnet chains. On the basis of the experimental results with bulk PMN-PT substrates, we estimate that the energy dissipation for logic operations in a reasonably scaled system using thin films will be a mere ∼1 aJ/bit.
The actuation and sensing behavior of a typical polycrystalline Fe81.6Ga18.4 alloy sample grown using free stand zone melt (FSZM) manufacturing processes was characterized and its cross-section texture was determined at three transverse stations using electron back-scattering diffraction (EBSD). An attempt was made to model the actuation and sensing behavior of the polycrystalline magnetostrictive sample from its cross-section texture by treating the polycrystal as composed of multiple grains of single crystals, each with a different orientation to the loading axis. The polycrystalline magnetomechanical behavior was modeled as the sum of the volume fraction weighted single-crystal behavior along the [100], [110], [210], [310], [111], [211] and [311] directions, which are modeled using the energy-based approach discussed in Armstrong (1997 J. Appl. Phys. 81 2321) and Atulasimha (2006 PhD Thesis Aerospace Engineering, University of Maryland).
Strain-mediated voltage control of magnetization in piezoelectric/ferromagnetic systems is a promising mechanism to implement energy-efficient spintronic memory devices. Here, we demonstrate giant voltage manipulation of MgO magnetic tunnel junctions (MTJ) on a Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) piezoelectric substrate with (001) orientation. It is found that the magnetic easy axis, switching field, and the tunnel magnetoresistance (TMR) of the MTJ can be efficiently controlled by strain from the underlying piezoelectric layer upon the application of a gate voltage. Repeatable voltage controlled MTJ toggling between high/low-resistance states is demonstrated. More importantly, instead of relying on the intrinsic anisotropy of the piezoelectric substrate to generate the required strain, we utilize anisotropic strain produced using local gating scheme, which is scalable and amenable to practical memory applications. Additionally, the adoption of crystalline MgO-based MTJ on piezoelectric layer lends itself to high TMR in the strain-mediated MRAM devices. *Corresponding author. Tel: (612) 625-9509. E-mail: jpwang@umn.edu 2 Information storage technology is constantly challenged by an increasing demand for storage units that are small, retain information for the longest time, and dissipate miniscule amount of energy to store (write) and retrieve (read) information. Magnetic random access memory (MRAM) meets these requirements to a large extent and has been proposed as a universal storage device for computer memory. [1][2][3] In MRAM technology, magnetic tunneling junctions (MTJ) comprise the main storage cells. Low-energy writing of bits requires an electrically tunable mechanism to reorient the magnetization of the MTJ. However, the widely studied switching mechanisms based on utilizing current induced spin-transfer-torques (STT) 4,5 or spin-orbit-torques (SOT) 6-8 incur high energy dissipation because of the relatively large writing current density. 9,10In recent years, several mechanisms based on using voltage to control magnetization have emerged as promising routes for ultra-low power writing of data. 11-15 Among these approaches, the strain induced control of the magnetic anisotropy in multiferroic heterostructures (a magnetostrictive layer elastically coupled with an underlying piezoelectric layer) stands out as a remarkably energyefficient switching mechanism. 16-21It has been widely investigated in various piezoelectric/ferromagnetic bilayer thin films [22][23][24][25][26] or nano-structures. [27][28][29][30] There are also several theoretical predications 31-33 that such a method will dissipate only a few atto-Joules (aJ) of energy to write data. This establishes the promise of using strain to control the resistance of an MTJ for ultra-energy-efficient memory applications.The key for strain control of the in-plane magnetization is that the in-plane strain should be anisotropic. In most of the previous reports, [24][25][26][27]34 single crystalline piezoelectric substrates Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.