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Magnetoresistance Effects and Their Application to Spintronic Devices

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 December 2017) | Viewed by 31025

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Special Issue Editors

Prof. Dr. Koki Takanashi

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Guest Editor

Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendal 980-77, Japan
Interests: spintronics; nanomagnetism; ordered alloys

Prof. Dr. Atsufumi Hirohata

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Guest Editor

Center for Science and Innovation in Spintronics, Tohoku University, Sendai 980-8577, Japan
Interests: spintronics; half-metallic ferromagnets; quantum nanoelectronics; nano-spintronic devices
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Half-metallic ferromagnets have been attracting intensive research in the view of realising an ideal 100% spin-polarised ferromagnet at room temperature. Among such ferromagnets, Heusler alloys have the greatest potential due to their high Curie temperatures, good lattice matching with major substrates, large minority-spin band-gap, and large magnetic moments in general. In this Special Issue, we focus on their magnetoresistance, in both vertical and lateral junctions, formed with a non-magnetic metallic or insulating layer. These junctions can be implemented in a read sensor in a hard disk drive or in a cell of magnetic random access memory to improve their recording density and operation efficiency. We intend to cover from theory and fundamentals of such junctions to their applications.

Prof. Dr. Koki Takanashi
Prof. Dr. Atsufumi Hirohata
Guest Editors

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Keywords

heusler alloys
giant magnetoresistance
tunnel magnetoresistance
half-metallic ferromagnets

Published Papers (5 papers)

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Research

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9 pages, 558 KiB

Open AccessArticle

Interface Tailoring Effect for Heusler Based CPP-GMR with an L1₂-Type Ag₃Mg Spacer

by Takahide Kubota, Yusuke Ina, Zhenchao Wen and Koki Takanashi

Materials 2018, 11(2), 219; https://doi.org/10.3390/ma11020219 - 31 Jan 2018

Cited by 5 | Viewed by 4321

Abstract

Current perpendicular-to-plane (CPP) giant magnetoresistance (GMR) effects are of interest in a possible application of magnetic sensor elements, such as read-head of hard disk drives. To improve the junction performance, the interface tailoring effects were investigated for the Heulser alloy, Co₂Fe [...] Read more.

L 1_{2}

-Ag₃Mg ordered alloy spacer. Ultra-thin Fe or Mg inserts were utilized for the CFMS/Ag₃Mg interfaces, and CPP-GMR at low bias current density, J and the J dependence were evaluated for the junctions. Although, at low bias J, MR ratio decreased with increasing the inserts thickness, the device output at high bias J exhibited quite weak dependence on the insert thickness. The output voltages of the order of 4 mV were obtained for the junctions regardless of the insert at an optimal bias J for each. The critical current density

J_{c}

was evaluated by the shape of MR curves depending on J.

J_{c}

increased with the insert thicknesses up to 0.45 nm. The enhancement of

J_{c}

suggests that spin-transfer-torque effect may reduce in the junctions with inserts, which enables a reduction of noise and can be an advantage for device applications. Full article

(This article belongs to the Special Issue Magnetoresistance Effects and Their Application to Spintronic Devices)

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8 pages, 826 KiB

Open AccessFeature PaperArticle

Spin Absorption Effect at Ferromagnet/Ge Schottky-Tunnel Contacts

by Michihiro Yamada, Yuichi Fujita, Shinya Yamada, Kentarou Sawano and Kohei Hamaya

Materials 2018, 11(1), 150; https://doi.org/10.3390/ma11010150 - 17 Jan 2018

Cited by 1 | Viewed by 4785

Abstract

We study the influence of the junction size in ferromagnet (FM)/semiconductor (SC) contacts on four-terminal nonlocal spin signals in SC-based lateral spin-valve (LSV) structures. When we use FM/Ge Schottky-tunnel junctions with relatively low resistance-area products, the magnitude of the nonlocal spin signal depends clearly on the junction size, indicating the presence of the spin absorption effect at the spin-injector contact. The temperature-dependent spin signal can also be affected by the spin absorption effect. For SC spintronic applications with a low parasitic resistance, we should consider the influence of the spin absorption on the spin-transport signals in SC-based device structures. Full article

(This article belongs to the Special Issue Magnetoresistance Effects and Their Application to Spintronic Devices)

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6109 KiB

Open AccessArticle

Electronic Energy Meter Based on a Tunnel Magnetoresistive Effect (TMR) Current Sensor

by Enrique García Vidal, Diego Ramírez Muñoz, Sergio Iván Ravelo Arias, Jaime Sánchez Moreno, Susana Cardoso, Ricardo Ferreira and Paulo Freitas

Materials 2017, 10(10), 1134; https://doi.org/10.3390/ma10101134 - 26 Sep 2017

Cited by 27 | Viewed by 8065

Abstract

In the present work, the design and microfabrication of a tunneling magnetoresistance (TMR) electrical current sensor is presented. After its physical and electrical characterization, a wattmeter is developed to determine the active power delivered to a load from the AC 50/60 Hz mains line. Experimental results are shown up to 1000 W of power load. A relative uncertainty of less than 1.5% with resistive load and less than 1% with capacitive load was obtained. The described application is an example of how TMR sensing technology can play a relevant role in the management and control of electrical energy. Full article

(This article belongs to the Special Issue Magnetoresistance Effects and Their Application to Spintronic Devices)

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Review

Jump to: Research

18 pages, 3444 KiB

Open AccessReview

Perpendicular Magnetic Anisotropy in Heusler Alloy Films and Their Magnetoresistive Junctions

by Atsufumi Hirohata, William Frost, Marjan Samiepour and Jun-young Kim

Materials 2018, 11(1), 105; https://doi.org/10.3390/ma11010105 - 11 Jan 2018

Cited by 40 | Viewed by 7692

Abstract

For the sustainable development of spintronic devices, a half-metallic ferromagnetic film needs to be developed as a spin source with exhibiting 100% spin polarisation at its Fermi level at room temperature. One of the most promising candidates for such a film is a Heusler-alloy film, which has already been proven to achieve the half-metallicity in the bulk region of the film. The Heusler alloys have predominantly cubic crystalline structures with small magnetocrystalline anisotropy. In order to use these alloys in perpendicularly magnetised devices, which are advantageous over in-plane devices due to their scalability, lattice distortion is required by introducing atomic substitution and interfacial lattice mismatch. In this review, recent development in perpendicularly-magnetised Heusler-alloy films is overviewed and their magnetoresistive junctions are discussed. Especially, focus is given to binary Heusler alloys by replacing the second element in the ternary Heusler alloys with the third one, e.g., MnGa and MnGe, and to interfacially-induced anisotropy by attaching oxides and metals with different lattice constants to the Heusler alloys. These alloys can improve the performance of spintronic devices with higher recording capacity. Full article

(This article belongs to the Special Issue Magnetoresistance Effects and Their Application to Spintronic Devices)

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1838 KiB

Open AccessReview

Optically Tunable Magnetoresistance Effect: From Mechanism to Novel Device Application

by Pan Liu, Xiaoyang Lin, Yong Xu, Boyu Zhang, Zhizhong Si, Kaihua Cao, Jiaqi Wei and Weisheng Zhao

Materials 2018, 11(1), 47; https://doi.org/10.3390/ma11010047 - 28 Dec 2017

Cited by 17 | Viewed by 5123

Abstract

The magnetoresistance effect in sandwiched structure describes the appreciable magnetoresistance effect of a device with a stacking of two ferromagnetic layers separated by a non-magnetic layer (i.e., a sandwiched structure). The development of this effect has led to the revolution of memory applications during the past decades. In this review, we revisited the magnetoresistance effect and the interlayer exchange coupling (IEC) effect in magnetic sandwiched structures with a spacer layer of non-magnetic metal, semiconductor or organic thin film. We then discussed the optical modulation of this effect via different methods. Finally, we discuss various applications of these effects and present a perspective to realize ultralow-power, high-speed data writing and inter-chip connection based on this tunable magnetoresistance effect. Full article

(This article belongs to the Special Issue Magnetoresistance Effects and Their Application to Spintronic Devices)

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