Field-Emission Enhanced Contacts for Disordered Semiconductor based Thin-Film Transistors

Magnetic skyrmions are chiral, topologically-protected magnetic spin textures known for their rich physics and potential for future data storage devices. Recently, magnetic multilayers with interfacial Dzyaloshinskii-Moriya interactions (DMI) have attracted great attention because they can support stable Néel-type magnetic skyrmions at room temperature. Here, we report on micromagnetic simulations of the effect of initial magnetic field treatment on skyrmion formation in [Pt/Co/Ir]n magnetic multilayers. The multilayer system was modeled with MuMax3 using parameters determined from experimental measurements on [Pt/Co/Ir]n=3,5,8 multilayer thin films. The simulations show that the application and subsequent removal of a nearly in-plane magnetic field can transition the originally labyrinth domains into bubble skyrmions, which agrees well magneto-optical Kerr effect imaging results. Systematic simulations of the magnetic configuration of the [Pt/Co/Ir]n as a function of angle and magnitude of the applied magnetic field reveal that the formation of bubble skyrmions occurs for field magnitudes that are close to but below the in-plane saturating field and that an additional out-of-plane component will help the skyrmion formation. Skyrmion formation is observed over a wider magnetic field range as the repetition number is increased, which corresponds to increasing importance of the demagnetization field coupling. Work at Bryn Mawr College was supported by the National Science Foundation CAREER DMR-1053854 and DMR-1708790. Work at Colorado State University was supported by the National Science Foundation DMR-1709525 and work at Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Science, Materials Science and Engineering Division.

**References:**



**Images:**

 The effects of field history on magnetic skyrmion formation in [Pt/Co/Ir]n multilayers.

We report a spin Hall magnetoresistance (SMR)-based spin-torque ferromagnetic resonance (ST-FMR) study of SOT efficiency in perpendicularly magnetized W/CoFeB/MgO structures, as shown in Fig. 1(a). A full analysis of the ST-FMR spectrum is developed for the PMA sample. The typical ST-FMR spectrum of PMA system shows two resonance modes, i.e., in-plane and out-of-plane magnetization precession modes, as shown in Fig.1(b). The damping-like torque efficiency of −0.31 is obtained from the angular dependence of symmetric and antisymmetric components of the out-of-plane resonance mode, as shown in Fig1(d-f), in which the significant contribution of spin-pumping-induced inverse spin Hall effect (ISHE) is carefully considered. The SOT efficiencies for the samples without PMA are also determined as reference values (ξDL = −0.35 and ξFL = −0.05) by analyzing the FM thickness dependence of SOT efficiency. By performing the modulation of damping measurement for the in-plane mode, the damping-like torque efficiency is determined to be -0.38, which is consistent with the reference value. The obtained values of damping-like torque efficiency by different means are consistent with each other. The present work provides useful insights to determine the damping-like torque efficiency of the PMA sample via ST-FMR measurements.

**References:**

[1] L. Q. Liu, Chi-Feng Pai, Y. Li, et al., Science 336, 555 (2012). [2] C. He, G. Yu, C. Grezes, et al., Phys. Rev. Appl. 10, 034067 (2018).

**Images:**

![](https://assets.underline.io/uploads/markdown_image/1/image/4b4d858c62e2d5cf3970f37ac86ac273.jpg)
FIG. 1. (a) The schematic of ST-FMR measurements setup including a bias tee, a microwave signal generator and a lock-in amplifier. The Jc denotes the charge current undergoing the sample, and the Js denotes the spin current along the normal direction of films. The external field H is applied in the plane at angle φ with respect to the X axis. (b) Experimental ST-FMR spectra for the perpendicular magnetized sample with tFM = 1.0 nm measured at the angle φ = 63o. The angular dependence of symmetric (c), (e) and antisymmetric (d), (f) components of the IP and OOP mode, respectively.

 Characterization of Spin-Orbit Torque Efficiency in Magnetic Heterostructures with Perpendicular Magnetic Anisotropy via Spin Torque Ferromagnetic Resonance

(DRC) Session 8 - Thin Film Devices

technical paper

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For almost eight decades, the Device Research Conference (DRC) has brought together leading scientists, researchers and students to share their latest discoveries in device science, technology and modeling. Notably, many of the first public disclosures of key device technologies were made at the DRC. This year marks the 79th anniversary of the DRC—the longest running device research meeting in the world. As we commemorate this meeting, the high-caliber technical sessions will be highlighted by plenary talks and invited talks by international research pioneers and leaders behind modern electronic technology.

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DRC 2021

For almost eight decades, the Device Research Conference (DRC) has brought together leading scientists, researchers and students to share their latest discoveries in device science, technology and modeling. Notably, many of the first public disclosures of key device technologies were made at the DRC. This year marks the 79th anniversary of the DRC—the longest running device research meeting in the world. As we commemorate this meeting, the high-caliber technical sessions will be highlighted by plenary talks and invited talks by international research pioneers and leaders behind modern electronic technology.

*Session Co-Chair: Daria Gusakova, SPINtronique et Technologie des Composants*

*Session Co-Chair: Joo-Von Kim, Université Paris-Saclay*

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AE: Micromagnetic Modelling

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Presentations

Field-Emission Enhanced Contacts for Disordered Semiconductor based Thin-Film Transistors

The effects of field history on magnetic skyrmion formation in [Pt/Co/Ir]n multilayers.

Characterization of Spin-Orbit Torque Efficiency in Magnetic Heterostructures with Perpendicular Magnetic Anisotropy via Spin Torque Ferromagnetic Resonance

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