Description: Description: Description: IEEE Santa Clara Valley Section  

Description: Description: Description: IEEE Magnetics Society

IEEE Magnetics Society
Santa Clara Valley Chapter
Meeting Presentation Summary



Tuesday, April 22nd, 2014

Western Digital, 1710 Automation Parkway, San Jose, CA
Directions and Map

Cookies, Conversation & Pizza too at 6:45 P.M.
Presentation at
7:30 P.M.

Spin-Caloritronics and Spin-Transfer-Torque Switching in Magnetic Nanostructures

Dr. Guenter Reiss
Universitaet Bielefeld, Germany



Spin-electronics and -caloritronics are rapidly developing research fields and many new phenomena such as magnetically perpendicular tunnel junctions (P-MTJs) [1, 2], the Spin-Seebeck-Effect (SSE, [3, 4]) and the Tunneling-Magneto-Seebeck-Effect (TMS, [5, 6]) have been observed. Because thermal effects are very important for the Spin-Transfer-Torque (STT) switching of MTJs, this talk will link results on thermally induced currents and voltages in ferromagnets and MTJs with STT-switching of CoFeB/MgO/CoFeB P-MTJs.

As an introduction to the field of spin-caloritronics, we first present results on the Longitudinal SSE of semi-conductive nickel ferrites [7]. In this material, the competing Anomalous Nernst Effect (ANE) can be strongly influenced by changing the conductivity of the ferromagnet and thus a direct comparison of LSSE and ANE becomes possible.

The second part will discuss the tunneling magnetoresistance (TMR) and the tunneling magneto-Seebeck effect (TMS) detected on magnetic tunnel junctions. We present results on the TMS obtained by two heating methods, discuss time-resolved experiments [8] and the influence of an uncertainty of input parameters such as temperature profiles on the effect. In addition, we demonstrate that an applied bias voltage strongly changes the observed TMS and discuss the results on the base of the electrode’s band-structures. For P-MTJs with ultrathin CoFeB electrodes and MgO barriers with thickness down to 4 monolayers, we discuss the STT-switching mechanisms and demonstrate, that extremely low switching currents for classical Spin-Transfer-Torque switching down to around 2.104A/cm² are possible by controlling the P-MTJ’s temperature. In relation with the thermally driven spin currents, the possibility to achieve sizeable thermally driven STT will be evaluated [2].



[1] S. Ikeda et al., Nat. Mat. 9, (2010) 721

[2] J. C. Leutenantsmeyer,, SPIN 03 (2013) 1350002

[3] K. Uchida,, Nat. Mat. 9, (2010) 894

[4] K. Uchida,, Appl. Phys. Lett. 97 (2010) 172505

[5] N. Liebing,, Phys. Rev. Lett. 107 (2011) 177201

[6] M. Walter,, Nat. Mater. 10 (2011) 742

[7] D. Meier,, Phys. Rev. B 87 (2013) 054421.

[8] A. Boehnke,, Rev. Sci. Instrum. 84 (2013) 063905.



Prof. Dr. Guenter Reiss is currently a professor for experimental physics at Bielefeld University, Germany. Dr. Reiss obtained his PhD in experimental physics from Regensburg University, Germany in 1989, and has since worked at research institutions including Regensburg University and IBM Watson Research Center. Dr. Reiss has served as the head of the thin film department at the institute for solid state and materials research at Dresden Germany from 1992 to 1997, and became a professor at Bielefeld University on 1997.


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