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Title: Influence of MgO Barrier Quality on Spin-Transfer Torque in Magnetic Tunnel Junctions

Abstract

Here, we studied the bias dependence of spin transfer torque in the MgO-based magnetic tunnel junction using a field-modulated spin torque ferromagnetic resonance measurement technique for three devices with tunneling magnetoresistances (MRs) of 60%, 67%, and 73%, respectively. The devices with a lower MR ratio showed the presence of multiple modes, while the device with higher MR (73%) showed a single resonance mode. We found a lower out-of-plane torkance in our devices compared to the in-plane torkance. The out-of-plane torque is linear with applied bias, while the bias dependence of in-plane torque shows a strong dependence on the MR ratio and hence the barrier quality.

Authors:
 [1];  [1];  [2];  [3];  [1]
  1. Indian Inst. of Technology (IIT), Delhi (India). Dept. of Physics
  2. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division
  3. Univ. of Gothenburg (Sweden). Dept. of Physics; KTH Royal Inst. of Technology, Stockholm (Sweden). Materials and NanoPhysics, School of Engineering Sciences
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); India Department of Science and Technology; Swedish Foundation for Strategic Research (SSF)
OSTI Identifier:
1419948
Grant/Contract Number:
AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 112; Journal Issue: 2; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Spintronics; Magnetic tunnel junctions; Ferromagnetic resonance; Magnetic ordering; Electrical properties

Citation Formats

Tiwari, Dhananjay, Sharma, Raghav, Heinonen, O. G., Akerman, J., and Muduli, P. K.. Influence of MgO Barrier Quality on Spin-Transfer Torque in Magnetic Tunnel Junctions. United States: N. p., 2018. Web. doi:10.1063/1.5005893.
Tiwari, Dhananjay, Sharma, Raghav, Heinonen, O. G., Akerman, J., & Muduli, P. K.. Influence of MgO Barrier Quality on Spin-Transfer Torque in Magnetic Tunnel Junctions. United States. doi:10.1063/1.5005893.
Tiwari, Dhananjay, Sharma, Raghav, Heinonen, O. G., Akerman, J., and Muduli, P. K.. 2018. "Influence of MgO Barrier Quality on Spin-Transfer Torque in Magnetic Tunnel Junctions". United States. doi:10.1063/1.5005893.
@article{osti_1419948,
title = {Influence of MgO Barrier Quality on Spin-Transfer Torque in Magnetic Tunnel Junctions},
author = {Tiwari, Dhananjay and Sharma, Raghav and Heinonen, O. G. and Akerman, J. and Muduli, P. K.},
abstractNote = {Here, we studied the bias dependence of spin transfer torque in the MgO-based magnetic tunnel junction using a field-modulated spin torque ferromagnetic resonance measurement technique for three devices with tunneling magnetoresistances (MRs) of 60%, 67%, and 73%, respectively. The devices with a lower MR ratio showed the presence of multiple modes, while the device with higher MR (73%) showed a single resonance mode. We found a lower out-of-plane torkance in our devices compared to the in-plane torkance. The out-of-plane torque is linear with applied bias, while the bias dependence of in-plane torque shows a strong dependence on the MR ratio and hence the barrier quality.},
doi = {10.1063/1.5005893},
journal = {Applied Physics Letters},
number = 2,
volume = 112,
place = {United States},
year = 2018,
month = 1
}

Journal Article:
Free Publicly Available Full Text
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  • Magnetization switching induced by spin transfer torque is used to write magnetic memories (Magnetic Random Access Memory, MRAM) but can be detrimental to the reading process. It would be quite convenient therefore to modulate the efficiency of spin transfer torque. A solution is adding an extra degree of freedom by using double barrier magnetic tunnel junctions with two spin-polarizers, with controllable relative magnetic alignment. We demonstrate, for these structures, that the amplitude of in-plane spin transfer torque on the middle free layer can be efficiently tuned via the magnetic configuration of the electrodes. Using the proposed design could thus pavemore » the way towards more reliable read/write schemes for MRAM. Moreover, our results suggest an intriguing effect associated with the out-of-plane (field-like) spin transfer torque, which has to be further investigated.« less
  • Magnetic tunnel junctions for spin-transfer torque (STT) switching are prepared to investigate the dielectric breakdown. Intact and broken tunnel junctions are characterized by transport measurements prior to transmission electron microscopy analysis. The comparison to our previous model for thicker MgO tunnel barriers reveals a different breakdown mechanism arising from the high current densities in a STT device: instead of local pinhole formation at a constant rate, massive electromigration and heating leads to displacement of the junction material and voids are appearing. This is determined by element resolved energy dispersive x-ray spectroscopy and three dimensional tomographic reconstruction.
  • The thermal spin-transfer torque (TSTT) is an effect to switch the magnetic free layer in a magnetic tunnel junction by a temperature gradient only. We present ab initio calculations of the TSTT. In particular, we discuss the influence of magnetic layer composition by considering Fe{sub x}Co{sub 1–x} alloys. Further, we compare the TSTT to the bias voltage driven STT and discuss the requirements for a possible thermal switching. For example, only for very thin barriers of 3 monolayers MgO, a thermal switching is imaginable. However, even for such a thin barrier, the TSTT is still too small for switching atmore » the moment and further optimization is needed. In particular, the TSTT strongly depends on the composition of the ferromagnetic layer. In our current study, it turns out that at the chosen thickness of the ferromagnetic layer, pure Fe gives the highest thermal spin-transfer torque.« less
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