High temperature annealing induced superparamagnetism in CoFeB/MgO/CoFeB tunneling junctions

Xiaoming Kou; Weigang Wang; Xin Fan; Lubna R. Shah; Rae Tao; John Q. Xiao

doi:10.1063/1.3496663

High temperature annealing induced superparamagnetism in CoFeB/MgO/CoFeB tunneling junctions

Xiaoming Kou
, Weigang Wang
, Xin Fan
, Lubna R. Shah
, Rae Tao
, John Q. Xiao

Research output: Contribution to journal › Article › peer-review

10 Scopus citations

Abstract

We have investigated the evolution of the magnetic transport properties as a function of short annealing time in CoFeB/MgO/CoFeB based magnetic tunnel junctions (MTJs) with a free layer of 2 nm. It is found that the hysteresis behaviors in magnetoresistance (MR) loops disappear in samples annealed for 17 min. The linear region between MR and the applied field gradually increases. The MR loops without hysteresis can be well fitted by using the superparamagnetism theory, suggesting the formation of superparamagnetic particles in the free layer during the high temperature annealing. The control of MTJ properties with annealing time is desirable in magnetic field sensor productions.

Original language	English (US)
Article number	083901
Journal	Journal of Applied Physics
Volume	108
Issue number	8
DOIs	https://doi.org/10.1063/1.3496663
State	Published - Oct 15 2010
Externally published	Yes

ASJC Scopus subject areas

General Physics and Astronomy

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10.1063/1.3496663

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@article{d0f1951635f740c381845dccd2cfe5c6,

title = "High temperature annealing induced superparamagnetism in CoFeB/MgO/CoFeB tunneling junctions",

abstract = "We have investigated the evolution of the magnetic transport properties as a function of short annealing time in CoFeB/MgO/CoFeB based magnetic tunnel junctions (MTJs) with a free layer of 2 nm. It is found that the hysteresis behaviors in magnetoresistance (MR) loops disappear in samples annealed for 17 min. The linear region between MR and the applied field gradually increases. The MR loops without hysteresis can be well fitted by using the superparamagnetism theory, suggesting the formation of superparamagnetic particles in the free layer during the high temperature annealing. The control of MTJ properties with annealing time is desirable in magnetic field sensor productions.",

author = "Xiaoming Kou and Weigang Wang and Xin Fan and Shah, \{Lubna R.\} and Rae Tao and Xiao, \{John Q.\}",

note = "Funding Information: The characterization and analyses related work was supported by DOE under Grant No. DEFG02-07ER46374 and the sampling fabrication was supported by NSF under Grant No. DMR0827249. FIG. 1. TMR ratio and coercivity as a function of annealing time for a single MTJ junction annealed at 460 ° C . FIG. 2. Measured MR loops of a MTJ junction annealed for different times at 460 ° C . FIG. 3. The linear region in MR loops as a function of annealing time. The TMR ratios are also labeled. FIG. 4. Measured MR loops of an MTJ junction annealed for 20 min at 460 ° C , φ is the angle between the applied magnetic field and the pinning direction. The solid line is the fitting based on the superparamagnetism theory. FIG. 5. Conductances in parallel and antiparallel states as a function of annealing time for the MTJ used in Fig. 1 annealed at 460 ° C . The inserted picture shows the I–V curves of another MTJ junction annealed at the same temperature for 1 and 40 min. ",

year = "2010",

month = oct,

day = "15",

doi = "10.1063/1.3496663",

language = "English (US)",

volume = "108",

journal = "Journal of Applied Physics",

issn = "0021-8979",

publisher = "American Institute of Physics",

number = "8",

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TY - JOUR

T1 - High temperature annealing induced superparamagnetism in CoFeB/MgO/CoFeB tunneling junctions

AU - Kou, Xiaoming

AU - Wang, Weigang

AU - Fan, Xin

AU - Shah, Lubna R.

AU - Tao, Rae

AU - Xiao, John Q.

N1 - Funding Information: The characterization and analyses related work was supported by DOE under Grant No. DEFG02-07ER46374 and the sampling fabrication was supported by NSF under Grant No. DMR0827249. FIG. 1. TMR ratio and coercivity as a function of annealing time for a single MTJ junction annealed at 460 ° C . FIG. 2. Measured MR loops of a MTJ junction annealed for different times at 460 ° C . FIG. 3. The linear region in MR loops as a function of annealing time. The TMR ratios are also labeled. FIG. 4. Measured MR loops of an MTJ junction annealed for 20 min at 460 ° C , φ is the angle between the applied magnetic field and the pinning direction. The solid line is the fitting based on the superparamagnetism theory. FIG. 5. Conductances in parallel and antiparallel states as a function of annealing time for the MTJ used in Fig. 1 annealed at 460 ° C . The inserted picture shows the I–V curves of another MTJ junction annealed at the same temperature for 1 and 40 min.

PY - 2010/10/15

Y1 - 2010/10/15

N2 - We have investigated the evolution of the magnetic transport properties as a function of short annealing time in CoFeB/MgO/CoFeB based magnetic tunnel junctions (MTJs) with a free layer of 2 nm. It is found that the hysteresis behaviors in magnetoresistance (MR) loops disappear in samples annealed for 17 min. The linear region between MR and the applied field gradually increases. The MR loops without hysteresis can be well fitted by using the superparamagnetism theory, suggesting the formation of superparamagnetic particles in the free layer during the high temperature annealing. The control of MTJ properties with annealing time is desirable in magnetic field sensor productions.

AB - We have investigated the evolution of the magnetic transport properties as a function of short annealing time in CoFeB/MgO/CoFeB based magnetic tunnel junctions (MTJs) with a free layer of 2 nm. It is found that the hysteresis behaviors in magnetoresistance (MR) loops disappear in samples annealed for 17 min. The linear region between MR and the applied field gradually increases. The MR loops without hysteresis can be well fitted by using the superparamagnetism theory, suggesting the formation of superparamagnetic particles in the free layer during the high temperature annealing. The control of MTJ properties with annealing time is desirable in magnetic field sensor productions.

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U2 - 10.1063/1.3496663

DO - 10.1063/1.3496663

M3 - Article

AN - SCOPUS:78149424919

SN - 0021-8979

VL - 108

JO - Journal of Applied Physics

JF - Journal of Applied Physics

IS - 8

M1 - 083901

ER -

High temperature annealing induced superparamagnetism in CoFeB/MgO/CoFeB tunneling junctions

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