APS March Meeting 2012
Volume 57, Number 1
Monday–Friday, February 27–March 2 2012;
Boston, Massachusetts
Session Y2: Invited Session: Magnetic Materials and Magnetism Research for Energy Applications
8:00 AM–11:00 AM,
Friday, March 2, 2012
Room: 204AB
Sponsoring
Units:
GMAG FIAP
Chair: Dario Arena, Brookhaven National Laboratory
Abstract ID: BAPS.2012.MAR.Y2.2
Abstract: Y2.00002 : Spintronics Device for Stand-by Power Free Nonvolatile CMOS VLSI*
8:36 AM–9:12 AM
Preview Abstract
Abstract
Author:
Hideo Ohno
(CSIS/RIEC, Tohoku University, Sendai, Japan)
Recent progress in perpendicular magnetic-easy axis magnetic tunnel
junctions (MTJs), a spintronics device, offers a high potential building
block for constructing not only stand-alone fast and nonvolatile RAMs in the
30 nm feature size and beyond but also nonvolatile CMOS VLSI employing
logic-in-memory architecture [1]. The shift from in-plane to perpendicular
is prompted by the need for a high crystalline anisotropy that is available
in perpendicular materials for reducing the device size. In addition,
current-induced switching is inherently more efficient with perpendicular
easy axis. However, satisfying both high tunnel magnetoresistance (TMR)
ratio over 100{\%} and low switching current was a challenge, because of the
mismatch between MgO (100) - CoFe(B) bcc (100) structure needed to obtain
high TMR and the crystal structure of perpendicular materials. It was shown
that a strong perpendicular interface anisotropy exists at the MgO-CoFeB
interface [2, 3], strong enough ($K_{i}$ = 1.3 mJ/m$^{2})$ to overcome
demagnetization energy and make the easy axis perpendicular when the
ferromagnetic electrode thickness is thin enough. First principle
calculation by Nakamura \textit{et al.} showed that the perpendicular anisotropy is due to
the oxygen-iron bond that reduces contribution of in-plane crystalline
anisotropy [4]. By the use of this perpendicular easy axis, a 40 nm$\phi $
MgO-CoFeB MTJ with high TMR ($>$100 {\%}) and low switching current of 49
$\mu $A was realized [2]. It was also pointed out that activation volume for
reversal plays an important role in determining the thermal stability of the
MTJs [5]. I will discuss how the MTJs are incorporated in CMOS VLSIs to make
them nonvolatile and stand-by power free.
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[1] S. Ikeda, \textit{et al.} IEEE Trans. Electron Devices, \textbf{54}, 991, 2007.
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[2] S. Ikeda, \textit{et al.} Nature Mat., \textbf{9}, 721, 2010.
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[3] M. Endo, \textit{et al.} Appl. Phys. Lett., \textbf{96}, 212503, 2010.
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[4] K. Nakamura \textit{et al}., Phys. Rev. B, 81, 220409(R), 2010
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[5] H. Sato, \textit{et al. }Appl. Phys. Lett. \textbf{99}, 042501, 2011.
*This work is supported by the FIRST program of JSPS.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.MAR.Y2.2