Design Concept of MAS Effect Dominant MAMR Head and Numerical Study

Takagishi, M.; Narita, Naoyuki; Iwasaki, H.; Suto, Hirofumi; Maeda, Takeshi; Takeo, Akihiko

doi:10.1109/tmag.2020.3027601

Cited by 21 publications

(6 citation statements)

References 8 publications

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“…56,57 Therefore, improving the areal density (AD) of the magnetic recording in HDDs is crucial for the development of a sustainable society in the era of big data. Energy-assisted magnetic recording technologies, such as heat-assisted magnetic recording (HAMR) [58][59][60] and microwave-assisted magnetic recording (MAMR) [61][62][63][64] , have demonstrated an ultrahigh AD up to over 2 Tbit/in 2 , which is approximately twice of that of today's HDDs. This requires the reader technology to have superior reading resolution and SNR.…”

Section: Magnetic Recording and Requirements For Reader Technologymentioning

confidence: 99%

Perspective on nanoscale magnetic sensors using giant anomalous Hall effect in topological magnetic materials for read head application in magnetic recording

Nakatani,

Kulkarni,

Suto

et al. 2024

Applied Physics Letters

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Recent advances in the study of materials with topological electronic band structures have revealed magnetic materials exhibiting giant anomalous Hall effects (AHEs). The giant AHE has not only attracted the research interest in its mechanism but also opened up the possibility of practical application in magnetic sensors. In this article, we describe simulation-based investigations of AHE magnetic sensors for applications to read head sensors (readers) of hard disk drives. With the shrinking of magnetic recording patterns, the reader technology, which currently uses multilayer-based tunnel magnetoresistance (TMR) devices, is associated with fundamental challenges, such as insufficient spatial resolution and signal-to-noise ratio (SNR) in sensors with dimensions below 20 nm. The structure of an AHE-based device composed of a single ferromagnetic material is advantageous for magnetic sensors with nanoscale dimensions. We found that AHE readers using topological ferromagnets with giant AHE, such as Co2MnGa, can achieve a higher SNR than current TMR readers. The higher SNR originates from the large output signal of the giant AHE as well as from the reduced thermal magnetic noise, which is the dominant noise in TMR readers. We highlight a major challenge in the development of AHE readers: the reduction in the output signal due to the shunting of the bias current and the leakage of the Hall voltage through the soft magnetic shields surrounding the AHE reader. We propose reader structures that overcome this challenge. Finally, we discuss the scope for future research to realize AHE readers.

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Section: Magnetic Recording and Requirements For Reader Technologymentioning

confidence: 99%

Perspective on nanoscale magnetic sensors using giant anomalous Hall effect in topological magnetic materials for read head application in magnetic recording

Nakatani,

Kulkarni,

Suto

et al. 2024

Applied Physics Letters

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“…This characteristic is advantageous to devices demanding strong STT, such as spin-torque oscillators for energy-assisted writing in hard-disk-drive applications, in which oscillation of large magnetic volumes is crucial. [18][19][20][21][22][23] Tunnel magnetoresistance (TMR) studies on Fe 4 N and Fe 3 O 4 have reported large negative MR over −50% at room temperature, demonstrating the negative spin polarization of these materials. 24,25 Similarly, giant magnetoresistance (GMR) studies reported that materials such as CoFeGd, FeCr, FeV, NiCr, and Fe 4 N have negative spin polarization.…”

Section: Introductionmentioning

confidence: 99%

Negative spin polarization of Mn2VGa Heusler alloy thin films studied in current-perpendicular-to-plane giant magnetoresistance devices

Suto,

Barwal,

Simalaotao

et al. 2024

Journal of Applied Physics

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Magnetic materials with high negative spin polarization have been sought as a building block to increase the design freedom and performance of spintronics devices. In this paper, we investigate negative spin polarization of Mn2VGa Heusler alloy in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices. We fabricated an epitaxial CPP-GMR stack consisting of Mn2VGa/Ag/CoFe with L21 ordering in the Mn2VGa layer and observed negative magnetoresistance (MR), which provided evidence of negative spin polarization. The MR ratio depended on thermal treatments (deposition at an elevated temperature and post-annealing), because these processes affected the ordering, roughness, and magnetic properties of Mn2VGa. The maximum MR ratio reached −1.8% at room temperature and −3.0% at low temperatures, representing the highest among the negative MR values in pseudo-spin-valve CPP-GMR devices despite the underestimation due to an incomplete antiparallel magnetization configuration. These findings demonstrate the potential of Mn2VGa for a material with high negative spin polarization.

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“…In the proposed devices, negative P materials are used to generate a spin-polarized current whose spin polarity is opposite to the magnetization direction. 8,9) The use of negative P materials can exert spin-transfer torque (STT) of the desired direction in the case where standard positive P materials work oppositely and disturb device operation.…”

mentioning

confidence: 99%

“…Due to this advantage, CPP-GMR structures have been explored for STT devices for next-generation hard disk drives. 8,9,[22][23][24][25][26][27] In this paper, we propose and demonstrate a simple method to evaluate STT efficiency in CPP-GMR devices, which utilizes magnetization reversal against a magnetic field by introducing a DC bias current. The proposed method was applied to FeCr, a promising material with negative P, to estimate its STT efficiency.…”

mentioning

confidence: 99%

Evaluation of spin-transfer-torque efficiency using magnetization reversal against a magnetic field: comparison of FeCr with negative spin polarization and NiFe

Suto¹,

Nakatani²,

Asam³

et al. 2023

Appl. Phys. Express

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We propose and demonstrate an experimental method to evaluate spin-transfer-torque (STT) efficiency in current-perpendicular-to-plane giant magnetoresistance devices, which utilizes STT-induced magnetization reversal against a perpendicular magnetic field. Using, this method, we estimated the STT efficiency of FeCr with negative spin polarization, which attracts attention in spintronics applications. In comparison with NiFe with positive spin polarization, the sign of the STT from FeCr was opposite, reflecting negative spin polarization. The STT efficiency of FeCr was approximately half that of NiFe at room temperature and surpassed that of NiFe at 50 K.

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Design Concept of MAS Effect Dominant MAMR Head and Numerical Study

Cited by 21 publications

References 8 publications

Perspective on nanoscale magnetic sensors using giant anomalous Hall effect in topological magnetic materials for read head application in magnetic recording

Perspective on nanoscale magnetic sensors using giant anomalous Hall effect in topological magnetic materials for read head application in magnetic recording

Negative spin polarization of Mn2VGa Heusler alloy thin films studied in current-perpendicular-to-plane giant magnetoresistance devices

Evaluation of spin-transfer-torque efficiency using magnetization reversal against a magnetic field: comparison of FeCr with negative spin polarization and NiFe

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