2 Magnetic Domain Wall Motion memory Magnetic race-track memoryStuart Parkin, “Magnetic race-track – a novel storage class spintronic memory”, Intern J. Mod. Physics B 22 (2008) 117Spin torque transfer MRAMShould we consider storage-class memories in ERD?Does is belong to PIDS or to ERD?MRAM has been transferred from ERDto PIDS in 2003
3 Selection criteria for new technology entries candidates
4 “Minimum Requirement” Criteria The ‘minimum requirements’ criteria for a new technology to be considered as a candidate for ERD chapter is sufficient research activity, e.g.the technology is explored by several research groups, orThere is an extensive research activity of one groupThere are at least 2 publications in peer-reviewed journals
5 General ‘Loose’ Criteria Potential for scalingRoadmap DriverOn-chip integrated solutionsPotential for embedded applicationsOutstanding research issues existGuidelines for the research community and government funding agenciesNot in productionInnovation phase
7 Conventional MRAM FM free layer W FM pinned layer MRAM element is operated by magnetic field generated from current lines in the proximity of MTJFM free layerWFM pinned layer“Wireless communication”Proximity effects – crosstalkScaling issue, Heat, reliability etc.
8 MRAM Scaling issueT. Kawahara et al, “2Mb SPRAM (Spin-Transfer Torque RAM)…”, IEEE J. Solid-State Circ. 43 (2008) 109Hitachi groupScaling issue: Conventional MRAM needs a larger current for smaller dimensions
9 Spin-torque switching Injected spin-polarized electrons interact with the magnetic moment of a free layer and transfer their angular momentumIf sufficient current is applied, the exerted spin torque switches the free layer either parallel or anti-parallel to the pinned layer depending on the direction of flow of the currentAttractive for memory array applications,does not have the magnetic half-select problemsmaller switching currentSpin torque transfer RAM (ST-RAM)MTJ for spin-torque switching
10 MTJ for spin-torque switching MTJ is operated by spin polarized current passing through MTJInjection efficiencyW~Nat~L2Scaling promise: spin-torque MRAM needs a smaller current for smaller dimensions
11 MRAM and ST-MRAM Scaling Reciprocal Scaling Relations
14 Outstanding research issues Theory:Critical current issueIc needs to be decreasedFrom 107 A/cm2 to 105 A/cm2New material structuresMTJ current needs to be increasedNew MTJ designInjection efficiency“Although the presence of spin torque has been unambiguously observed, its quantitative behavior in MTJ, especially its bias dependence has yet to be understood in detail”J. C. Sankey et al., Nature Physics 4 (2008) IBM group
15 New concepts are needed Nano-current-channel (NCC) injectionFeSiO layer with columnar NCC structureCurrent can pass through NCC onlyProvide magnetic nucleation points and induce the free layer switching through the growth of the nucleation points
16 General ‘Loose’ Criteria Discussion: Spin torque transfer MRAM Does is belong to PIDS or to ERD?MRAM has been transferred from ERDto PIDS in 2003Potential for scalingRoadmap DriverOn-chip integrated solutionsPotential for embedded applicationsOutstanding research issues existGuidelines for the research community and government funding agenciesNot in productionInnovation phase
18 Magnetic Domain Wall Motion memory Current-driven magnetic domain wall (DW) motionDWMDWM occurs in a submicron-size ferromagnetic stripeCharge carriers become polarized by the interaction between conduction electrons and local magnetic momentsExert torque on the magnetic moments within DWSensed by TMR or GMR device
21 Magnetic Race-track Memory A proposal for a novel storage-class memory, in which magnetic domains are used to store information in a “magnetic race-track”Shift register schemeA solid state memory with storage capacity same/better than HDDImproved performance and reliabilityThe magnetic race track is comprised of tall columns of magnetic material arranged perpendicularly to the Si surfaceThe domains are moved up and down by current pulses~ns pulsesSensing by magnetic tunnel junction device
29 Main Issue Due to the high current densities, strong heating occurs DW transformations have been shown to originate not only from spin torque effects but also from thermal excitationsFor applications, it is a key requirement to devise ways for efficient cooling
30 There is a considerable interest in DWM IBMSamsungHitachiSeagateCanon
31 Outstanding research issues The capacity of spin-polarized current to move a domain wall was experimental established, butThe mechanisms responsible for that motion remain under debateCurrent density needs to be decreased!
Your consent to our cookies if you continue to use this website.