From Nanoelectronics to Nano-Spintronics

Abstract

Today's electronics uses electron charge as a state variable for logic and computing operation, which is often represented as voltage or current. In this representation of state variable, carriers in electronic devices behave independently even to a few and single electron cases. As the scaling continues to reduce the physical feature size and to increase the functional throughput, two most outstanding limitations and major challenges, among others, are power dissipation and variability as identified by ITRS. This paper presents the expose, in that collective phenomena, e.g., spintronics using appropriate order parameters of magnetic moment as a state variable may be considered favorably for a new room-temperature information processing paradigm. A comparison between electronics and spintronics in terms of variability, quantum and thermal fluctuations will be presented. It shows that the benefits of the scalability to smaller sizes in the case of spintronics (nanomagnetics) include a much reduced variability problem as compared with today's electronics. In addition, another advantage of using nanomagnets is the possibility of constructing nonvolatile logics, which allow for immense power savings during system standby. However, most of devices with magnetic moment usually use current to drive the devices and consequently, power dissipation is a major issue. We will discuss approaches of using electric-field control of ferromagnetism in dilute magnetic semiconductor (DMS) and metallic ferromagnetic materials. With the DMSs, carrier-mediated transition from paramagnetic to ferromagnetic phases make possible to have devices work very much like field effect transistor, plus the non-volatility afforded by ferromagnetism. Then we will describe new possibilities of the use of electric field for metallic materials and devices: Spin wave devices with multiferroics materials. We will also further describe a potential new method of electric field control of metallic ferromagnetism via field effect of the Thomas Fermi surface layer.

Low-power non-volatile spintronic memory: STT-RAM and beyond

“…The discovery of the possibility to manipulate and induce switching of the magnetization by spin-polarized currents via the STT effect [9,10] in nanomagnets has been the key motivating force behind the recent rise of interest in MRAM, and particularly STT-RAM [17,18]. STT-RAM conserves the advantages of Oersted-field-switched (toggle) MRAM (high speed, very high endurance, non-volatility), but the currentdriven switching mechanism makes STT-RAM more scalable and allows for smaller switching energies (on the order of ∼100 fJ) compared with Oersted-field-switched MRAM, as will be discussed later.…”

Current-induced spin-orbit torque switching of perpendicularly magnetized Hf|CoFeB|MgO and Hf|CoFeB|TaOx structures

“…The manipulation of magnetization in thin ferromagnetic layers using an in-plane electric current, which generates spin-orbit-torque (SOT) on the magnetic moments, is being explored as an alternative way to perform writing in magnetic tunnel junctions (MTJs), 1 with improved energy efficiency, reliability, and density compared to magnetic field-based and spin-transfer torque (STT)-based methods. [2][3][4][5][6][7][8][9][10][11] The current-induced SOTs generated in heavymetal (HM) j ferromagnet (FM) j oxide layer (OX) structures can be quantified in terms of internal effective magnetic fields acting on the magnetic moments. These SOTs have been attributed to the spin-Hall effect (SHE), the Rashba effect, or unknown mechanisms in various experiments.…”

Metallosupramolecular grid complexes: towards nanostructured materials with high-tech applications

“…Consequently, researchers have investigated the application of ''bottom-up'' approaches (supramolecular chemistry), or a combination of both ''top-down'' and ''bottom-up'' approaches for the preparation of nanoscale electronic devices. [148][149][150][151] The physicochemical properties of metallosupramolecular grid complexes have been identified as being particularly promising for nanoscale electronic devices. 34 Two dimensional arrays of electronically and magnetically active structures are of particular interest for the next generation of nanoscale electronic devices, 152 and one aspect of relevance to the transfer of metallogrids from laboratory-based studies to high-tech applications is their orientation relative to an underlying substrate to which they may be attached, particularly for applications in which well-organized arrays of addressable metal ions are of interest.…”

“…124 Towards application as nanoscale electronic/ spintronic devices As noted above, two dimensional arrays of electronically and magnetically active structures are of particular interest for the next generation of nanoscale electronic/spintronic devices. 143,[148][149][150][169][170][171][172][173] Conductance switching in molecular junctions is useful for data storage elements in dynamic random access memory circuits, and the [2 Â 2] Co(II) metallogrids formed from ligand 23 have potential for such applications (see Fig. 17).…”