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Hysteresis Loops of Magnetically Coupled Multilayers - Experiment and Calculations
M. Czapkiewicz,T. Stobiecki,R. Rak,J. Wrona,C. G. Kim 한국자기학회 2004 Journal of Magnetics Vol.9 No.2
In this paper calculations of magnetisation and magnetoresistance characteristics of the Spin Valve (SV) and Pseudo Spin Valve (PSV) spintronics structures are reported and compared with the experimental data. The magnetisation reversal process was analysed with respect to the Stoner-Wohlfahrt model of total surface energy in terms of uniaxial anisotropy, exchange coupling between ferromagnetic layers, unidirectional exchange anisotropy of pinned layer (modelled by exchange coupling between magnetisation of pinned layer and net magnetisation of antiferromagnetic layer with high anisotropy). The numerical simulation of the model to the experimental magnetisation data yielded the above parameters for SV and PSV structures. These parameters were used to more sophistically micromagnetic modelling tool originating from the project called Object Oriented Micromagnetic Framework. Influence of the shape anisotropy of the Magnetic Tunnelling Junction cell used in MRAM was simulated by means of micromagnetic simulations. Results were compared to those obtained from the spot Kerr measurements.
Interlayer and Interfacial Exchange Coupling of IrMn Based MTJ
J. Wrona,T. Stobiecki,M. Czapkiewicz,J. Kanak,R. Rak,M. Tsunoda,M. Takahashi 한국자기학회 2004 Journal of Magnetics Vol.9 No.2
As deposited and annealed MTJs with the structure of Ta(5 ㎚)/Cu(10 ㎚)/Ta(5 ㎚)/Ni_(80)Fe_(20)(2 ㎚)/Cu(5 ㎚)/Ir_(25)Mn_(7.5)(10 ㎚)/Co_(70)Fe_(30)(2.5 ㎚)/Al-O/Co_(70)Fe_(30)(2.5 ㎚)/Ni_(80)Fe_(20)(t)/Ta(5 ㎚), where t = 10, 30, 60 and 100 ㎚ were characterized by XRD and magnetic hysteresis loops measurements. The XRD measurements were done in grazing incidence (GID scan-2θ) and θ-2θ geometry, by rocking curve (scan-ω) and pole figures in order to establish correlation between texture and crystallites size and magnetic parameters of exchange biased and interlayer coupling. The variations of shifting and coercivity field of free and pinned layers after annealing in 300℃ correlate with the improvement of [111] texture and grains size of Ni_(80)Fe_(20) and Ir_(25)Mn_(75) respectively. The exchange biased and the coercivity fields of the pinned layer linearly increased with increasing grain size of Ir_(25)Mn_(75). The reciprocal proportionality between interlayer coupling and coercivity fields of the free layer and grain size of Ni_(80)Fe_(20) was found. The enhancement of interlayer coupling between pinned and free layers, after annealing treatment, indicates on the correlated in-phase roughness of dipolar interacting interfaces due to increase of crystallites size of Ni_(80)Fe_(20).
The Structure, and the Magnetic and Magnetoresistive Characteristics of the Spin Valve Multilayers
T. Stobiecki,M. Czapkiewicz,J. Wrona,W. PowroŸnik,F. Stobiecki 한국자기학회 1998 Journal of Magnetics Vol.3 No.3
In this paper we report the low and high angle diffraction results, and the magnetic and magnetoresistive characteristics of the spin valve multilayer structure prepared by the sputter machine Emerald II in the Balzers Laboratory. The investigated system consists of a ferromagnetic free layer (7 ㎚ NiFe) and a ferromagnetic pinned layer (7 ㎚ NiFe), separated from each other by a nonmagnetic (2.1 ㎚ Cu) spacer. The NiFe pinned layer is fixed by the exchange coupling with an antiferromagnetic layer (10 ㎚ FeMn). For such system the magnetoresistance ratio ΔR/R=3.58%, the interlayer exchange coupling He=6.4 Oe and the field sensitivity 1.15%/Oe were otained.