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Title: Comparison of the chemical heterogeneities and microstructure between CoFeB/MgO/CoFeB and CoFeB/Al-O/CoFeB magnetic tunnel junctions.

Abstract

No abstract prepared.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
982609
Report Number(s):
ANL/MSD/CP-58870
TRN: US201015%%1219
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Conference
Resource Relation:
Journal Name: Microscopy and Microanalysis; Journal Volume: 13; Journal Issue: 2 ; 2007; Conference: Microscopy & Microanalysis 2007 Meeting; Aug. 5, 2007 - Aug. 9, 2007; Ft. Lauderdale, FL
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 59 BASIC BIOLOGICAL SCIENCES; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; MEETINGS; MICROANALYSIS; MICROSCOPY; MICROSTRUCTURE; TUNNELS

Citation Formats

Sudbrack, C. K., Chiaramonti, A. N., Hiller, J. M., Egelhoff, Jr., W. F., Petford-Long, A. K., Materials Science Division, and NIST. Comparison of the chemical heterogeneities and microstructure between CoFeB/MgO/CoFeB and CoFeB/Al-O/CoFeB magnetic tunnel junctions.. United States: N. p., 2007. Web.
Sudbrack, C. K., Chiaramonti, A. N., Hiller, J. M., Egelhoff, Jr., W. F., Petford-Long, A. K., Materials Science Division, & NIST. Comparison of the chemical heterogeneities and microstructure between CoFeB/MgO/CoFeB and CoFeB/Al-O/CoFeB magnetic tunnel junctions.. United States.
Sudbrack, C. K., Chiaramonti, A. N., Hiller, J. M., Egelhoff, Jr., W. F., Petford-Long, A. K., Materials Science Division, and NIST. Mon . "Comparison of the chemical heterogeneities and microstructure between CoFeB/MgO/CoFeB and CoFeB/Al-O/CoFeB magnetic tunnel junctions.". United States. doi:.
@article{osti_982609,
title = {Comparison of the chemical heterogeneities and microstructure between CoFeB/MgO/CoFeB and CoFeB/Al-O/CoFeB magnetic tunnel junctions.},
author = {Sudbrack, C. K. and Chiaramonti, A. N. and Hiller, J. M. and Egelhoff, Jr., W. F. and Petford-Long, A. K. and Materials Science Division and NIST},
abstractNote = {No abstract prepared.},
doi = {},
journal = {Microscopy and Microanalysis},
number = 2 ; 2007,
volume = 13,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • The effect of B concentration on the tunneling magnetoresistance (TMR) of (Co{sub 25}Fe{sub 75}){sub 100-x}B{sub x}/MgO/(Co{sub 25}Fe{sub 75}){sub 100-x}B{sub x} (x = 22 and 33) pseudo-spin-valve (P-SV) magnetic tunnel junctions (MTJs) was investigated. The TMR ratios for optimally annealed MTJs with x = 22 and 33 were 340% and 170%, respectively, at room temperature. High resolution transmission electron microscopy (HRTEM) observation showed a weaker (001) texture in the MgO barrier in the MTJ with x = 33. The bottom electrode was not fully crystallized even with a considerable amount of B in the (Co{sub 25}Fe{sub 75}){sub 67}B{sub 33}, while goodmore » epitaxy was observed between (001) textured MgO and (Co{sub 25}Fe{sub 75}){sub 78}B{sub 22} electrodes.« less
  • Significant lateral compositional variations have been revealed in a three-dimensional atom probe (3DAP) study of the MgO barriers of magnetic tunnel junctions. High resolution electron microscopy of the CoFeB/MgO/CoFeB/Ru/CoFe/PtMn multilayer indicates that the MgO barrier is smooth, uniform, and with good crystallinity. Nevertheless, the 3DAP data show lateral variations in the MgO composition over length scales on the order of tens of nanometers. Boron is not uniformly distributed within the CoFeB layers, but has tended to segregate to the interfaces. Annealing has no significant effect on the distribution of B, indicating that the segregation occurring during growth is relatively stable.
  • For sputteredCoFeB/MgO/CoFeB magnetic tunnel junctions, it is well known that the tunnelmagnetoresistance (TMR) ratio increases with increasing annealing temperature (Ta) up to a critical value (Tp), and then decreases with further increasing Ta , resulting in a peak around Tp. The improved crystallinity of the MgO barrier and CoFeB electrodes due to annealing has been considered as the main reason for the enhancement of the TMR ratio, especially for Ta < Tp. In this work, the evidence is provided that the magnon excitation plays a great contribution to the magnetoresistance (MR) behavior in annealed samples based on the measurement ofmore » dynamic conductance and inelastic electron tunneling (IET) spectra. The magnon activation energy (Ec) obtained from the fits for IET spectra exhibits a similar temperature dependence with that of the TMR ratio. A detailed analysis shows that the magnon excitation, together with improved crystallinity of the MgO barrier and CoFeB layers, is the main contribution to the annealing-temperature-dependent MR behavior.« less
  • Magnetic tunnel junctions (MTJs) comprising Ta(5)/NiFe(5)/IrMn(15)/CoFeB(5)/Mg(1)/MgO(3.5)/ CoFeB(5)/Ta(5)/Ag(20) (thickness in nm) with (110) oriented CoFeB layers are grown using dual ion beam sputtering. The tunnel magnetoresistance (TMR) of MTJs is found to be significantly bias dependent and exhibits zero bias anomaly (ZBA) which is attributed to the presence of magnetic impurities or diffusion of Mn from antiferromagnetic IrMn in the barrier. Adjacent to the ZBA, two peaks at 24 ± 3 mV and 34 ± 3 mV are also observed, which differ both in intensity as well as their position in the antiparallel and parallel magnetic states, suggesting that they are due to magnon excitations. In additionmore » to this, a phonon peak at 65 ± 3 mV is also observed. The effect of temperature on the inelastic and elastic tunneling contributions is studied in detail in 25–300 K range using the Glazman and Matveev model. Ten series of localized states are found to be involved in hopping conduction in the forbidden gap of MgO barrier. The effect of presence of such inelastic channels is found to be insignificant at low temperatures yielding sizeable enhancement in TMR.« less
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