Multilevel-3D Bit Patterned Magnetic Media with 8 Signal Levels Per Nanocolumn

Amos, Nissim; Butler, John; Lee, Beomseop; Shachar, Meir H.; Hu, Bing; Tian, Yuan; Hong, Jeongmin; Garcia, Davil; Ikkawi, R.; Haddon, Robert C.; Litvinov, Dmitri; Khizroev, Sakhrat

doi:10.1371/journal.pone.0040134

Cited by 27 publications

(11 citation statements)

References 11 publications

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“…This includes GMR and TMR spin valves [ 35 ] for magnetic sensors, magnetoresistive random access memory (MRAM) cells and a multitude of systems that are based on spin-transfer torque. The large parameter range of coercivities and easy axes orientations possible in one single device will lead to qualitative advances, e.g., new types of 3D multilevel magnetic memory cells [ 36,37 ] and the design of switchable ferromagnetic/nonmagnetic hybrid structures (e.g., ferromagnet/superconductor hybrids [ 38 ] ).…”

Section: Discussionmentioning

confidence: 99%

Spin‐Structured Multilayers: A New Class of Materials for Precision Spintronics

Schlage

Bocklage

Erb

et al. 2016

Adv Funct Materials

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7423wileyonlinelibrary.com extensively explored to maximize the magnitude of the magnetoresistive signal, which is defi ned as the normalized difference of the electrical resistance in the antiparallel and parallel magnetic confi guration of the trilayer. The basic GMR and TMR characteristics of spintronic devices and thus their functionalities, however, did not signifi cantly change during the last decade. This is due to conventional magnetic multilayer design and its limitations based on the interplay of accessible magnetic anisotropy contributions. Here, we show that oblique incidence deposition (OID) can be used in an elegant way to achieve full control on the magnetic anisotropy in every individual layer of such magnetoresistive multilayer stacks for the fi rst time. The additional shape anisotropy component introduced via OID allows for arbitrarily crossed magnetic easy axes with adjustable switching fi elds and opens a path for customized spintronic devices with conceptually new functionalities.So far, two major approaches have been pursued to engineer fi eld-dependent relative magnetic confi gurations of two ferromagnetic layers. In the fi rst case, one of the ferromagnetic layers either exhibits an enhanced coercive fi eld or is magnetically pinned (exchange biased) by an additional antiferromagnetic layer of high magnetic anisotropy. Thus, only the magnetically uncoupled free layer follows small external fi elds, causing a change of the magnetic confi guration and the magnetoresistance. [ 13 ] In the second approach, an interlayer exchange coupling, the Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction, is used to align both layers relative to each other. [ 14 ] The interlayer coupling defi nes the magnetic saturation behavior and hence the functionality of the trilayer. In conventional systems, only parallel or antiparallel orientations of the ferromagnetic layers are reliably achieved. Effi cient RKKY coupling is observed for particular material combinations only and depends very sensitively on the interlayer thickness. [ 15,16 ] Therefore, conventional magnetic multilayer design is restricted to a limited number of magnetic confi gurations in the trilayers which constrains the design and control of magnetic spin structures that are available for realizing particular magnetoelectronic responses.Our approach enables one to realize and tune magnetic and magnetoresistive properties in spintronic multilayer systems that exceed the potential of conventional approaches by far. The technique is not based on exchange-bias or interlayer coupling and is not affected by their limitations. Every ferromagnetic layer of arbitrary chemical composition, as a constituent either Spin-Structured Multilayers: A New Class of Materials for Precision SpintronicsKai Schlage , * Lars Bocklage , Denise Erb , Jade Comfort , Hans-Christian Wille , and Ralf Röhlsberger * Magnetoelectronic multilayer devices are widely used in today's information and sensor technology. Their functionality, however, is limited by the inherent prop...

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Section: Discussionmentioning

confidence: 99%

Spin‐Structured Multilayers: A New Class of Materials for Precision Spintronics

Schlage

Bocklage

Erb

et al. 2016

Adv Funct Materials

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“…This limit is around 1 Tbit per square inch for current perpendicular magnetic recording. [2][3][4][5] In order to further increase the recording density in future recording media new materials with the following properties are sought: (i) they should have large uniaxial magnetocrystalline anisotropy energy (MAE) K u , (ii) large saturation magnetization, (iii) fast magnetic response to external applied fields, and (iv) moderate Curie temperatures above the room temperature.…”

mentioning

confidence: 99%

Tuning the Curie temperature of FeCo compounds by tetragonal distortion

Jakobsson

Şaşıoğlu

Mavropoulos

et al. 2013

Applied Physics Letters

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Combining density-functional theory calculations with a classical Monte Carlo method, we show that for B2-type FeCo compounds tetragonal distortion gives rise to a strong reduction of the Curie temperature $T_{\mathrm{C}}$. The $T_{\mathrm{C}}$ monotonically decreases from 1575 K (for $c/a=1$) to 940 K (for $c/a=\sqrtwo$). We find that the nearest neighbor Fe-Co exchange interaction is sufficient to explain the $c/a$ behavior of the $T_{\mathrm{C}}$. Combination of high magnetocrystalline anisotropy energy with a moderate $T_{\mathrm{C}}$ value suggests tetragonal FeCo grown on the Rh substrate with $c/a=1.24$ to be a promising material for heat-assisted magnetic recording applications.Comment: 4 pages, 2 figure

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“…[ 26,27 ] However, despite all the progress, barely any research has been conducted to exploit the natural ability of nanomagnetic/spintronic devices to enable a new computing paradigm relying on 3D architectures capable of multilevel signal processing. [ 23,28 ] The idea of using a 3D space, instead of 2D surfaces as in the traditional devices, to store and process information is attractive not only because of the significantly increased data capacity by storing data across the thickness, but due to the capability to process information with multilevel signals.…”

Section: Figurementioning

confidence: 99%

A Dual Magnetic Tunnel Junction‐Based Neuromorphic Device

Hong

et al. 2020

Advanced Intelligent Systems

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Dennard scaling rule, which was proposed in 1974 and had been relevant for decades due to advances in the development of metal-oxide-semiconductor field-effect transistors (MOSFETs), has finally ran out of steam. [1,2] However, the need for energyefficient computing nowadays is even more urgent than ever before, covering numerous domains, such as large-scale sensor networks, Internet of Things (IoT), bioelectronics, and arguably, most importantly, neuromorphic computing applications. [3-18] While revisiting the reasons behind the failure of Dennard scaling rule, the following two major issues with the modern approach may be raised. First, the "Boltzmann limit," i.e., the statistical distribution of electrons in semiconductor energy bands sets the minimum ON/OFF switching for conventional transistors. The second is the "von Neumann bottleneck"; the performance of memory significantly lags behind that of the processor, which, in turn, leads to latency in conventional computer architectures. When higher performance is expected from the existing computer infrastructure, particularly, to simulate the brain architecture in neuromorphic computers, one would 1) sacrifice the leakage of transistors, e.g., by lowering the threshold voltage of a MOSFET, and/or 2) enlarge the size of memories, such as static random-access memories (SRAMs) and embedded dynamic random-access memories (DRAMs). However, both of the approaches result in an explosive use of chip energy consumption. With the drastic increase in device counts to meet the modern systems' requirements, it is critical to consider the development of a new building block with a fundamentally different mechanism as well as delivering a unified computingstorage functionality. [3,6,19,20] Spintronic devices have many unparalleled advantages, including data non-volatility, low operational power, radiation hardness, potential of scaling down to the sub-5 nm cell size, and natural inclination for multilevel 3D computing paradigms. [21-24] A primitive device structure for spintronics is the magnetic tunnel junction (MTJ) device, which consists of two ferromagnetic (FM) layers and a thin insulating layer (e.g., MgO) used as the tunneling barrier between the two FMs layers. Depending on the parallel (P) or anti-parallel (AP) relative orientation of the two FMs' magnetizations, the tunnel magnetoresistance (TMR) of an MTJ can be used as the read-out mechanism. As for the write mechanism, the spin-transfer torque (STT) carried by the injection current can be utilized to switch one of the FMs' magnetization, in analogy with the write process in a modern magnetization random-access memory (MRAM). [25] Recently, significant progress has been achieved to use separate paths for write and read operations in MRAMs, for example, by inducing spin-orbit torque (SOT) or voltage-controlled magnetization anisotropy (VCMA) effects, to further lower the operation energy and improve the write endurance. [26,27]

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Multilevel-3D Bit Patterned Magnetic Media with 8 Signal Levels Per Nanocolumn

Cited by 27 publications

References 11 publications

Spin‐Structured Multilayers: A New Class of Materials for Precision Spintronics

Spin‐Structured Multilayers: A New Class of Materials for Precision Spintronics

Tuning the Curie temperature of FeCo compounds by tetragonal distortion

A Dual Magnetic Tunnel Junction‐Based Neuromorphic Device

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