清華大學材料科學與工程研究院《材料科學論壇》

學術報告

報告題目：Thermally induced spin dynamics

報告人： Prof. Minori Goto（Osaka University）

報告時間：2019年8月23日（周五） 下午3:30

報告地點：清華大學逸夫技術科學樓A205學術報告廳

聯系人：宋成老師 62781275

歡迎廣大師生踴躍參加！

報告摘要：

Thermally induced spin dynamics is one of the significant natures for efficient spin control. Here we introduce the two topics, the heat driven spin torque in magnetic tunnel junctions and the Brownian motion of magnetic skyrmion by thermal fluctuation.

Heat driven spin torque is important for efficient spin control. However, in general, the heat engine in nanoscale system is inefficient because of rapid heat dissipation [1]. The low interfacial thermal conductivity enables to suppress heat dissipation and to enhance the efficiency of heat driven spin torque. The film stack, buffer layer | CoFeB(2) reference layer | MgO(1.1) | FeB(1.7) free layer | MgO(1.0) | cap layer, was deposited on Si | SiO2 substrate (nm in thickness). The Fe|MgO interface has low thermal conductivity [2] which enhances the temperature increase in free layer. The magnetic anisotropy change due to the Joule heating is measured by spin-torque diode technique [3]. We characterized the magnitude of heat controlled magnetic anisotropy (HCMA) as ?5.3 μJ/Wm, which is corresponding to the voltage controlled magnetic anisotropy of -300 fJ/Vm [4].

Second topic is the skyrmion Brownian motion. The Brownian computing has been proposed as ultralow power consumption technology using a small amount of energy close to the thermodynamic limit [5]. Magnetic skyrmions are suitable for the Brownian computer because they act as Brownian particles in solid state materials and are electrically controllable and detectable at room temperature. However, the usual skyrmion circuits fabricated by etching of the ferromagnetic film decrease the demagnetization field stabilizing the skyrmions, and thus prevent their formation. In this study, a skyrmion Brownian circuit implemented in a continuous ferromagnetic film with patterned SiO2 capping to stabilize the skyrmion formation [6]. This technique enables the efficient control of skyrmion-based Brownian computers, as well as memory and logic devices.

報告人簡介：

Personal data
Name : Minori Goto
Gender : Male  
Date of Birth : November 20th ,1986
Nationality : Japanese
Address : 1-3, Machikaneyamacho, Toyonaka, Osaka, 560-8531, Japan
Phone Number : +81-6-6850-6427
Email Address : goto@mp.es.osaka-u.ac.jp
URL : http://ysuzukilab.html.xdomain.jp/index_eng.html

Education
April 2005 – March 2009: Keio University, Kanagawa, Japan
  Faculty of Science and Technology
  Department of Physics
  Bachelor of Science
Modules included: Basic physics such as classical mechanics, quantum physics, electromagnetism, relativity theory, statistical physics, material physics, etc.

April 2009 – March 2011:Keio University, Kanagawa, Japan
 Graduate School of Science and Technology
 School of Fundamental Science and Technology
 Master of Science
Modules included:Spintronics, experiment, microfabrication, Electrical measurement, magnetization dynamics.

April 2012 – September 2012: Keio University, Kanagawa, Japan
 Graduate School of Science and Technology
 School of Fundamental Science and Technology
 Special student

September 2012 – March 2015: Keio University, Kanagawa, Japan
 Graduate School of Science and Technology
 School of Fundamental Science and Technology
 Doctor of Science
Modules included: Spintronics, experiment, microfabrication, Electrical measurement, magnetization dynamics.

Employment
April 2011–March 2012: Toshiba Corporation
 Engineer of Semiconductor Circuit Design

April 2015–March 2016:  Osaka University
 Graduate School of Engineering Science
Specially appointed assistant professor

April 2016–present: Osaka University
Graduate School of Engineering Science
Assistant professor