掲載種別：研究論文（学術雑誌）   出版者・発行元：AIP Publishing  

It is technically challenging to shrink the size of a tunneling magnetoresistance reader to below 20 nm for magnetic recording technology beyond 4 Tb/in2 due to its complex film stack. Recently, we proposed a reader architecture based on the inverse spin Hall effect to resolve those challenges, referred below as spin–orbit torque (SOT) reader, whose structure consists of a SOT layer and a ferromagnetic layer. However, the heavy metal-based SOT reader has small output voltage and low signal-to-noise ratio (SNR) due to the limited spin Hall angle θSH (< 1) of heavy metals. In this Letter, we demonstrate the integration of BiSb topological insulator with strong inverse spin Hall effect into the SOT reader that can significantly improve the output voltage and SNR. First, we theoretically calculate the noises in a 20 × 20 nm2 BiSb-based SOT reader to establish the relationships between SNR and θSH at various bias currents. We then demonstrate proof-of-concept BiSb-based SOT readers using CoFe/MgO/BiSb stack, which show large output voltages up to 15 mV at an input current of 9.4 kA/cm2 at room temperature. We project a giant θSH = 61 for BiSb. Our work demonstrates the potential of BiSb for SOT reader beyond 4 Tb/in2 magnetic recording technology.

DOI： 10.1063/5.0135831

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/tmag.2021.3115169

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掲載種別：研究論文（学術雑誌）   出版者・発行元：AIP Publishing  

Topological insulators (TIs) are promising for efficient spin current sources in spin–orbit torque (SOT) magnetoresistive random access memory (MRAM). However, TIs are usually deposited by molecular beam epitaxy on single crystalline III–V semiconductor or sapphire substrates, which are not suitable for realistic applications. Here, we studied SOT characteristics in sputtered BiSb topological insulator—Pt/Co/Pt—MgO heterostructures deposited on oxidized Si substrates, where Pt/Co/Pt trilayers have a large perpendicular magnetic anisotropy field of 4.5 kOe. We show that the BiSb layer has a large effective spin Hall angle of θSHeff = 2.4 and a high electrical conductivity of σ = 1.0 × 105 Ω−1 m−1. The magnetization can be switched by a small current density of 2.3 × 106 A cm−2 at a pulse width of 100 µs, which is 1 or 2 orders of magnitudes smaller than those in heavy metals. Our work demonstrates the high efficiency and robustness of BiSb as a spin current source in realistic SOT-MRAM.

DOI： 10.1063/5.0062625

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掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP Publishing  

Abstract

In this paper, we study the dynamics of ultracold ⁸⁷Rb under the influence of tilted optical lattice via Bloch oscillation in the single-band regime. By simulating the intraband dynamics of wavepacket in position and momentum spaces, the dependences of amplitude and period of the oscillation on tilted coefficient and lattice height are shown and compared with classical theory under tight-binding approximation. We also verify the limit of the single-band approximation where the Landau-Zener transition is neglected.

DOI： 10.1088/1742-6596/1506/1/012013

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その他リンク： https://iopscience.iop.org/article/10.1088/1742-6596/1506/1/012013

掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP Publishing  

DOI： 10.1088/1361-6404/aac99c

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その他リンク： https://iopscience.iop.org/article/10.1088/1361-6404/aac99c/pdf

掲載種別：研究論文（学術雑誌）   出版者・発行元：Hue University  

In this paper, we provide comprehensive study of the thermodynamic quantities of the ideal Fermi gas confined in a three-dimensional harmonic trap by using the properties of Fermi – Dirac integral function both analytically and numerically. The dependences of the chemical potential, total energy and heat capacity on the temperature are obtained via the appropriately approximated analytic formulae. Afterwards, the results are compared with the exact numerical ones in order to evaluate the applicability of these formulae.

DOI： 10.26459/hueuni-jns.v126i1b.4116

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