• Journal of the Korean Magnetics Society
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• v.12 no.4
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• pp.132-136
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• 2002

Enhancement of crystallinity and exchange bias characteristics for NiFe/FeMn/NiFe trilayer with Si buffer layer fabricated by ion-beam deposition were examined. A Si buffer layer promoted (111) texture of fcc crystallities in the initial growth region of NiFe layer deposited on it. FeMn layers deposited on Si/NiFe bilayer exhibited excellent (111) crystal texture. The antiferromagnetic FeMn layer between top and bottom NiFe films with the buffer Si 50 ${\AA}$-thick induced a large exchange coupling field Hex with a different dependence. It was found that H$\sub$ex/ of the bottom and top NiFe films with Si buffer layer revealed large value of about 110 Oe and 300 Oe, respectively. In the comparison of two Ta and Si buffer layers, the NiFe/FeMn/NiFe trilayer with Si could possess larger exchange coupling field and higher crystallinity.

• Journal of Magnetics
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• v.16 no.2
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• pp.83-87
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• 2011

The vortex-driven magnetization process of micron-sized, exchange-coupled square elements with composition of $Ni_{80}Fe_{20}$ (12 nm)/$Ir_{20}Mn_{80}$ (5 nm) is investigated. The exchange-bias is introduced by field-cooling through the blocking temperature (TB) of the system, whereby Landau-shaped vortex states of the $Ni_{80}Fe_{20}$ layer are imprinted into the $Ir_{20}Mn_{80}$. In the case of zero-field cooling, the exchange-coupling at the ferromagnetic/antiferromagnetic interface significantly enhances the vortex stability by increasing the nucleation and annihilation fields, while reducing coercivity and remanence. For the field-cooled elements, the hysteresis loops are shifted along the cooling field axis. The loop shift is attributed to the imprinting of displaced vortex state of $Ni_{80}Fe_{20}$ into $Ir_{20}Mn_{80}$, which leads to asymmetric effective local pinning fields at the interface. The asymmetry of the hysteresis loop and the strength of the exchange-bias field can be tuned by varying the strength of cooling field. Micromagnetic modeling reproduces the experimentally observed vortex-driven magnetization process if the local pinning fields induced by exchange-coupling of the ferromagnetic and antiferromagnetic layers are taken into account.

• Electrical & Electronic Materials
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• v.10 no.10
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• pp.1016-1021
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• 1997

Magneto resistance properties in spin-valve sandwiches with various thickness of nanmagnetic layer in contact with the ferromagnetic NiFe film were investigated. The NiFe layer in contact with the NiO film was pinned by strongly exchange-biased coupling and the free NiFe layer at the film surface induced a sharp change in the magnetoresistance at -5~15Oe due to small coercivity. The NiO/NiFe/Cu/NiFe film showed a magnetoresistance ratio in the range of 2.3~2.9% and a field sensitivity above 2.2%/Oe with various of nonmagnetic layer. The NiO/NiFe/Cu/NiFe film of the field sensitivity above 2.2%/Oe suggests stang possibility of magnetic sensor matter.

• Journal of Magnetics
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• v.1 no.1
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• pp.31-36
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• 1996

An externally applied magnetic field during heat treating the $Nd_2Fe_{14}B/Fe_3B$ based spring magnet was found to enhance the exchange coupling between the hard and soft magnetic grains. More than 30% increase in $M_r/M_s$ values for melt-spun $Nd_2Fe_{73.5}Co_3$$(Hf_{1-x}Ga_x)B_{18.5}$ (x=0, 0.5, 1) alloys was resulted from a uniform distribution of $Fe_3B, \alpha-Fe$ and $Nd_2Fe_{14}B$ phases, and also from a reduced grain size of those phases by 20%. The externally applied magnetic field induced a uniform distribution of fine grains. A study of Mossbauer effect also report that the enhancement of total magnetization of nanocomposite $Nd_2Fe_{14}B/Fe_3B$ alloys is attributed to an increased formation of $Fe_3$B after magnetic annealing.

• Journal of Magnetics
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• v.2 no.4
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• pp.143-146
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• 1997

The effects of deposition rate on exchange coupling field Hex and coercive field Hc in NiO spin-valves are discussed. The Hex and Hc increased with deposition rate of NiO film. The rms roughnesses of the NiO deposited at 6 ${\AA}$/min (NiO-Low) and 30${\AA}$/min (NiO-High) were almost similar, however, the short-range roughness increased with the deposition rate. The Hex, Hc and surface morphologies for the modulated NiO spin-valve films such as NiO-Low\NiO-High\NiO-Low and NiO-High\NiO-Low were investigated.

• Journal of Magnetics
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• v.14 no.3
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• pp.104-107
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• 2009

The effects of the magnetic property variation on current-induced magnetization switching in magnetic tunnel junction with perpendicular magnetic anistoropy (PMA) and the soft magnetic polarization-enhancement layers (PELs) inserted between the layers with PMA and the MgO layer was studied. A micromatnetic model was used to estimate the switching time of the free layer by different applied current densities, with changing saturation magnetization ($M_s$) of the PELs, interlayer exchange coupling between PMA layers and PELs. The switching time could be significantly reduced at low current densities, by increasing $M_s$ of PELs and decreasing interlayer exchange coupling.

• Journal of Magnetics
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• v.3 no.3
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• pp.92-95
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• 1998

In this paper we report the low and high angle diffraction results, and the magnetic and magnetroesistive 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 nm NiFe) and a ferromagnetic pinned layer (7 nm NiFe), separated from each other by a nonmagnetic (2.1 nm Cu) spacer. The NiFe pinned layer is fixed by the exchange coupling with an antiferromagnetic layer (10 nm FeMn). For such system the magnetoresistance ratio ΔR/R=3.58%, the interlayer exchange coupling $H_c=6.4$ Oe and the field sensitivity 1.15%/Oe were otained.

• Journal of Surface Science and Engineering
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• v.29 no.5
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• pp.386-392
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• 1996

The epitaxial TM/bcc-Cr(001) (TM=Fe, Co, Ni) multilayers have been prepared using MBE. The crystal structure, interlayer exchange coupling and magnetoresistance of those multilayers have been discussed. The structure of Fe, Co and Ni grown on bcc-Cr(001) exhibited bcc(001), distorted hcp(1120) and fcc(110), respectively. In Fe/Cr multilayes, an oscillatory exchange coupling has been observed, but not observed in Ni/Cr system, which may come from the large mixing at interfaces. Large MR ratio (116%, 4.2K) has been obtained in Fe/Cr system, but only 2% in Co/Cr system. This difference can be understood from the view point of the relative potential geight for down spin electrons between TM and Cr.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.45-48
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• 1998

We first report the GMR effect of new macroscopic ferrimagnet, Co-TbN. The Co-TbN system demonstrates typical macroscopic ferrimagnet properties which are a magnetic compensation Point and negative giant magnetoresistance (GMR) which is caused by the spin scattering contribution quite different from those of ordinary GMR materials. The Co-TbN system with 32 % TbN composition showed 0.72 % GMR in fields up to 8 kOe at room temperature and 9 % GMR at 250 K in 40 kOe. The GMR effect in the Co-TbN system increases with increasing temperature, which is due to the increase of ferromagnetic alignment of the Co and TbN in a field caused by the decrease of exchange coupling by temperature.

• Journal of Magnetics
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• v.9 no.2
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• pp.60-64
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• 2004

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.