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Title: Exchange coupling torque in ferrimagnetic Co/Gd bilayer maximized near angular momentum compensation temperature

Abstract

Highly efficient current-induced motion of chiral domain walls was recently demonstrated in synthetic antiferromagnetic (SAF) structures due to an exchange coupling torque (ECT). The ECT derives from the antiferromagnetic exchange coupling through a ruthenium spacer layer between the two perpendicularly magnetized layers that comprise the SAF. Here we report that the same ECT mechanism applies to ferrimagnetic bi-layers formed from adjacent Co and Gd layers. In particular, we show that the ECT is maximized at the temperature T A where the Co and Gd angular momenta balance each other, rather than at their magnetization compensation temperature T M. The current induced velocity of the domain walls is highly sensitive to longitudinal magnetic fields but we show that this not the case near T A. Our studies provide new insight into the ECT mechanism for ferrimagnetic systems. The high efficiency of the ECT makes it important for advanced domain wall based spintronic devices.

Authors:
 [1];  [1];  [2];  [3];  [4]; ORCiD logo [5];  [6]; ORCiD logo [7]; ORCiD logo [1]
  1. Max Planck Institute for Microstructure Physics, Halle (Saale) (Germany); Martin Luther Univ., Halle (Saale) (Germany)
  2. IBM Research–Almaden, San Jose, CA (United States)
  3. Max Planck Institute for Microstructure Physics, Halle (Saale) (Germany); Martin Luther Univ., Halle (Saale) (Germany); IBM Research–Almaden, San Jose, CA (United States)
  4. Max Planck Institute for Microstructure Physics, Halle (Saale) (Germany); Loughborough Univ., Leicestershire (United Kingdom)
  5. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  6. Univ. of California, Davis, CA (United States)
  7. Univ. of California, Davis, CA (United States); Georgetown Univ., Washington, D.C. (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1506384
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 9; Journal Issue: 1; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Bläsing, Robin, Ma, Tianping, Yang, See -Hun, Garg, Chirag, Dejene, Fasil Kidane, N’Diaye, Alpha T., Chen, Gong, Liu, Kai, and Parkin, Stuart S. P. Exchange coupling torque in ferrimagnetic Co/Gd bilayer maximized near angular momentum compensation temperature. United States: N. p., 2018. Web. doi:10.1038/s41467-018-07373-w.
Bläsing, Robin, Ma, Tianping, Yang, See -Hun, Garg, Chirag, Dejene, Fasil Kidane, N’Diaye, Alpha T., Chen, Gong, Liu, Kai, & Parkin, Stuart S. P. Exchange coupling torque in ferrimagnetic Co/Gd bilayer maximized near angular momentum compensation temperature. United States. doi:10.1038/s41467-018-07373-w.
Bläsing, Robin, Ma, Tianping, Yang, See -Hun, Garg, Chirag, Dejene, Fasil Kidane, N’Diaye, Alpha T., Chen, Gong, Liu, Kai, and Parkin, Stuart S. P. Mon . "Exchange coupling torque in ferrimagnetic Co/Gd bilayer maximized near angular momentum compensation temperature". United States. doi:10.1038/s41467-018-07373-w. https://www.osti.gov/servlets/purl/1506384.
@article{osti_1506384,
title = {Exchange coupling torque in ferrimagnetic Co/Gd bilayer maximized near angular momentum compensation temperature},
author = {Bläsing, Robin and Ma, Tianping and Yang, See -Hun and Garg, Chirag and Dejene, Fasil Kidane and N’Diaye, Alpha T. and Chen, Gong and Liu, Kai and Parkin, Stuart S. P.},
abstractNote = {Highly efficient current-induced motion of chiral domain walls was recently demonstrated in synthetic antiferromagnetic (SAF) structures due to an exchange coupling torque (ECT). The ECT derives from the antiferromagnetic exchange coupling through a ruthenium spacer layer between the two perpendicularly magnetized layers that comprise the SAF. Here we report that the same ECT mechanism applies to ferrimagnetic bi-layers formed from adjacent Co and Gd layers. In particular, we show that the ECT is maximized at the temperature TA where the Co and Gd angular momenta balance each other, rather than at their magnetization compensation temperature TM. The current induced velocity of the domain walls is highly sensitive to longitudinal magnetic fields but we show that this not the case near TA. Our studies provide new insight into the ECT mechanism for ferrimagnetic systems. The high efficiency of the ECT makes it important for advanced domain wall based spintronic devices.},
doi = {10.1038/s41467-018-07373-w},
journal = {Nature Communications},
number = 1,
volume = 9,
place = {United States},
year = {2018},
month = {11}
}

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Figures / Tables:

Fig. 1 Fig. 1: Magnetic properties of ferrimagnetic bilayer. a Temperature-dependent coercivity of Gd loops. b Temperature-dependent magnetic moments of Co and Gd. Co and Gd magnetic moments are normalized to their respective values at the transition temperature of 207.5 K. Error bar of the magnetic moments are estimated from the noisemore » and non-linear background of the XMCD spectrum. c Threshold field Hth at which the DWs start to move as a function of T (from Kerr microscopy). Red and blue dots indicate expansion of the up and down domains in the Co layer, respectively. Direction of DW motion is depicted in the inset in which the Co sublayer magnetization is shown. Dashed lines represent fit to the data by a hyperbola. d Schematic illustration of the DW configuration in the Co and Gd layers at T < TM, T = TM, T = TA and T > TA. mGd increases with decreasing T and compensates mCo at TM« less

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    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.