Manipulating Spin Current in the Magnetic Nanopillar

Because of the capability to switch the magnetization of a nanoscale magnet, the spin transfer effect is critical for the application of magnetic random access memory. For this purpose, it is important to enhance the spin current carried by the charge current. Calculations based on the diffusive spin-dependent transport equations reveal that the magnitude of spin current can be tuned by modifying the ferromagnetic layer and the spin relaxation process in the device. Increasing the ferromagnetic layer thickness is found to enhance both the spin current and the spin accumulation. On the other hand, a strong spin relaxation in the capping layer also increases the spin current but suppresses the spin accumulation. To demonstrate the theoretical results, nanopillar structures with the size of ∼100 nm are fabricated and the current-induced magnetization switching behaviors are experimentally studied. When the ferromagnetic layer thickness is increased from 3 nm to 20 nm, the critical switching current for the current-induced magnetization switching is significantly reduced, indicating the enhancement of the spin current. When the Au capping layer with a short spin-diffusion length replaces the Cu capping layer with a long spin-diffusion length, the reduction of the critical switching current is also observed.

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Spin Pumping in a Ferromagnetic/Nonmagnetic/Spin-Sink Trilayer Film: Spin Current Termination

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.508.266 ◽

2012 ◽

Vol 508 ◽

pp. 266-270 ◽

Cited By ~ 9

Author(s):

K. Harii ◽

Z. Qiu ◽

T. Iwashita ◽

Y. Kajiwara ◽

K. Uchida ◽

...

Keyword(s):

Diffusion Equation ◽

Hall Effect ◽

Spin Diffusion ◽

Diffusion Length ◽

Spin Current ◽

Interlayer Thickness ◽

Spin Pumping ◽

Charge Current ◽

Inverse Spin Hall Effect ◽

Spin Diffusion Length

A Spin Current Generated by Spin Pumping in a Ferromagnetic/Nonmagnetic/Spin-Sink Trilayer Film Is Calculated Based on the Spin Pumping Theory and the Standard Spin Diffusion Equation. By Attaching the Spin-Sink Layer, the Injected Spin Current Is Drastically Enhanced when the Interlayer Thickness Is Shorter than the Spin Diffusion Length of the Interlayer. We Also Provided the Formula of the Charge Current which Is Induced from the Pumped Spin Current via the Inverse Spin-Hall Effect.

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Energy-Efficient Multiferroic Spin-Devices and Spin-Circuits

SPIN ◽

10.1142/s2010324720300017 ◽

2020 ◽

Vol 10 (04) ◽

pp. 2030001

Author(s):

Kuntal Roy

Keyword(s):

Energy Efficient ◽

Large Scale ◽

Spin Diffusion ◽

Diffusion Length ◽

Spin Current ◽

Logic Gates ◽

Low Energy ◽

Circuit Representation ◽

Spin Diffusion Length ◽

Spin Devices

Spin-devices are switched by flipping spins without moving charge in space and this can lead to ultra-low-energy switching replacing traditional transistors in beyond Moore’s law era. In particular, the electric field-induced magnetization switching has emerged to be an energy-efficient paradigm. Here, we review the recent developments on ultra-low-energy, area-efficient, and fast spin-devices using multiferroic magnetoelectric composites. It is shown that both digital logic gates and analog computing with transistor-like high-gain region in the input-output characteristics of multiferroic composites are feasible. We also review the equivalent spin-circuit representation of spin-devices by considering spin potential and spin current similar to the charge-based counterparts using Kirchhoff’s voltage/current laws, which is necessary for the development of large-scale circuits. We review the spin-circuit representation of spin pumping, which happens anyway when there is a material adjacent to a rotating magnetization and therefore it is particularly necessary to be incorporated in device modeling. Such representation is also useful for understanding and proposing experiments. In spin-circuit representation, spin diffusion length is an important parameter and it is shown that a thickness-dependent spin diffusion length reflecting Elliott–Yafet spin relaxation mechanism in platinum is necessary to match the experimental results.

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Estimation of spin-diffusion length from the magnitude of spin-current absorption: Multiterminal ferromagnetic/nonferromagnetic hybrid structures

Physical Review B ◽

10.1103/physrevb.72.014461 ◽

2005 ◽

Vol 72 (1) ◽

Cited By ~ 168

Author(s):

T. Kimura ◽

J. Hamrle ◽

Y. Otani

Keyword(s):

Spin Diffusion ◽

Diffusion Length ◽

Spin Current ◽

Hybrid Structures ◽

Spin Diffusion Length

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Determination of Cobalt Spin-Diffusion Length in Co/Cu Multilayered Heterojunction Nanocylinders Based on Valet–Fert Model

Nanomaterials ◽

10.3390/nano11010218 ◽

2021 ◽

Vol 11 (1) ◽

pp. 218

Author(s):

Saeko Mizoguchi ◽

Masamitsu Hayashida ◽

Takeshi Ohgai

Keyword(s):

Layer Thickness ◽

Giant Magnetoresistance ◽

Spin Diffusion ◽

Diffusion Length ◽

Anodized Aluminum ◽

Anodized Aluminum Oxide ◽

Electrochemical Growth ◽

Potential Condition ◽

Spin Diffusion Length ◽

Sputter Deposited

Anodized aluminum oxide (AAO) nanochannels of diameter, D, of ~50 nm and length, L, of ~60 µm (L/D: approx. 1200 in the aspect ratio), were synthesized and applied as an electrode for the electrochemical growth of Co/Cu multilayered heterojunction nanocylinders. We synthesized numerous Co/Cu multilayered nanocylinders by applying a rectangular pulsed potential deposition method. The Co layer thickness, tCo, ranged from ~8 to 27 nm, and it strongly depended on the pulsed-potential condition for Co layers, ECo. The Cu layer thickness, tCu, was kept at less than 4 nm regardless of ECo. We applied an electrochemical in situ contact technique to connect a Co/Cu multilayered nanocylinder with a sputter-deposited Au thin layer. Current perpendicular-to-plane giant magnetoresistance (CPP-GMR) effect reached up to ~23% in a Co/Cu multilayered nanocylinder with ~4760 Co/Cu bilayers (tCu: 4 nm and tCo: 8.6 nm). With a decrease in tCo, (ΔR/Rp)−1 was linearly reduced based on the Valet–Fert equation under the condition of tF > lFsf and tN < lNsf. The cobalt spin-diffusion length, lCosf, was estimated to be ~12.5 nm.

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