• Journal of Magnetics
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• v.5 no.4
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• pp.139-142
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• 2000

The interlayer coupling between adjacent ferromagnetic layers was examined for CoFe/Cu/NiFe trilayer systems. A series of films of CoFe (20 nm)/Cu($t_{cu}$)/NiFe (20 nm) trilayers with Cu spacer thickness, $t_{cu}$, in the range of 1~10 m was deposited on Si(100) wafers at room temperature by DC magnetron sputtering. In order to understand the dependence of the magnetic interaction between ferromagnetic $Co_{90}Fe_{10}$ (wt.%) and $Ni_{81}Fe_{19}$ (wt.%) layers separated by a nonmagnetic Cu spacer on the Cu layer thickness, we investigated the derivative ferromagnetic resonance (FMR) spectra. The FMR results were analyzed using the model of Layadi and Art-man for interlayer interaction. The interlayer coupling constant decreases in an oscillatory manner as the Cu spacer thickness increases up to 10 nm and approaches zero above 10 nm. The interlayer coupling constant is positive for all samples. Hence, it seems that the exchange coupling between adjacent CoFe and NiFe layers separated by a Cu layer is ferromagnetic.

• Journal of the Korean Magnetics Society
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• v.18 no.6
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• pp.232-236
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• 2008

Dependence of interlayer exchange coupling on antiferromagnetic IrMn thickness, thermal stability, and parallel anisotropy angle in perpendicular anisotropy [CoFe/Pt/CoFe]/IrMn multilayers was investigated. The magnetic property of [CoFe($10{\AA}$)/Pt($8{\AA}$)/CoFe($10{\AA}$)] induced by antiferromagnetic ordering of IrMn layer was maintained a stable perpendicular anisotropy up to $250^{\circ}C$ and from $7{\AA}$ to $160{\AA}$ of IrMn thickness. The value of interlayer exchange coupling of [CoFe/Pt/CoFe]/IrMn multilayers with perpendicular anisotropy increased to 1.5 times at anisotropy angle of $60^{\circ}$ more than of $0^{\circ}$. On the other side, the interlayer exchange coupling at anisotropy angle of $90^{\circ}$ was $\infty$ Oe, it was likely diverted to a parallel shape magnetization.

• 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.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.229-229
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• 2003

Enhancement of the exchange bias and optimization of the structure have been the focus that many researchers studied, recently [1]. In this report, magnetic properties of MTJs with structure of Si/Ta (5)/Cu (10)/ Ta (5)/ Ni$\sub$80/Fe$\sub$20/ Cu (5)/ Mn$\sub$75Ir$\sub$25/ (10)/ Co$\sub$70/Fe$\sub$30/ (2.5)/ Al-O (1.5)/ Co$\sub$70/Fe$\sub$30/ (2.5)/ Ni$\sub$80/Fe$\sub$20/ (t)/ Ta (5) (t=0,10, 30, 60 and 100 nm, respectively) were investigated. The relationship between the structure and magnetic parameters of interfacial exchange coupling and interlayer coupling in as-deposited and annealed junctions was studied. The temperature dependence of exchange coupling was considered.

• Journal of the Korean Magnetics Society
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• v.16 no.2
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• pp.130-135
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• 2006

We theoretically demonstrate that the interlayer exchange coupling (IEC) energy can be manipulated by means of an external bias voltage in a $F_1/NM/F_2/S$$(F_1:ferromagnetic,\;NM:nonmagnetic\;metallic,\;F_2:ferromagnetic,\;S:semiconductor\;layers)$ four-layer system. It is well known that the IEC energy between two ferromagnetic layers separated by nanometer thick nonmagnetic layer depends on the spin-dependence of reflectivity to the $F_1/NM/F_2/S$ four-layer system, where the reflectivities at the interface in $NM/F_2$ interface also depends on $F_2/S$ interface due to the multiple reflection of an electron-like optics. Finally, the IEC energy depends on the spin-dependent electron reflectivity not only at the interfaces of $F_1/NM/F_2$, but also at the interface of $F_2/S$. Naturally the Schottky barrier is formed at the interface between metallic ferromagnetic layer and semiconductor, the Schottky barrier height and thickness can be tailored by an external bias voltage, which causes the change of the spin-dependent reflectivity at $F_2/S$ interface. We show that the IEC energy between two ferromagnetic layers can be controlled by an external bias voltage due ti the electron-optics nature using a simple free-electron-like one-dimensional model.

• Korean Journal of Materials Research
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• v.13 no.6
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• pp.369-373
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• 2003

Magneto-optic Kerr Effect(MOKE), AFM and magnetoresistance measurements have been carried out on as-deposited and annealed Magnetic Tunnel Junctions(MTJs) with junction sizes 180, 250, 320 and 380 $\mu\textrm{m}$ in order to investigate the correlation among interlayer exchange coupling, surface roughness and junction size. Relatively irregular variations of coercivity $H_{c}$ (∼17.5 Oe) and interlayer exchange coupling $H_{E}$ (∼17.5 Oe) are observed over the junction in as-deposited sample prepared by DC magnetron sputtering. After annealing at $200^{\circ}C$, $H_{c}$ decreases to 15 Oe, while $H_{ E}$ increases to 20 Oe with smooth local variation. $H_{E}$ shows very good correlation with surface roughness across the junction in agreement with Neel's orange peel coupling. The increasing slope per $\mu\textrm{m}$ of normalized $H_{c}$ and $H_{E}$ are same near junction edge along free-layer direction irrespective of junction size, giving relatively uniform $H_{c}$ and $H_{ E}$ for wider junction size. Thickness profiles of the junctions measured with $\alpha$-step show increasingly flat top surface for larger junctions, indicating better uniformity for large. junctions in agreement with the normalized$ H_{c}$ and H$/_{E}$ curves. TMR ratios also increase with increasing junction size, indicating improvement for larger uniform junctions.

• Journal of Magnetics
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• v.8 no.1
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• pp.13-17
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• 2003

The longitudinal magnetooptical Kerr effect was used to analyse magnetic domains in soft magnetic ${(Fe_{97}A1_3)}_{85}N_{15}$/$Al_{2}O_{3}$ multilayers in order to get microscopic understanding of interlayer exchange coupling. The measuring system consists of a Kerr microscope, a CCIR camera (with an 8-bit framegrabber), 16 bit digital camera and computer system for real-time image processing and to control external magnetic field and cameras. The strength of ferromagnetic (EM) coupling as a function of the spacer thickness of $Al_2O_3$ was investigated. It was found that strong FM-coupling, strong uniaxial anisotropy and coherent rotation of the magnetization have been observed for the spacer thickness in the range of 0.2 nm $\leq$ t $\leq$ 1 m, however, weak FM-coupling, patch domains and $360^{\circ}$-walls occur for the spacer thickness of t = 2.5 nm. At a spacer thickness of t $\geq$ 5 nm transition takes place from weak FM-coupling to the decoupled state where complex interlayer interactions and different types of the domain walls were observed.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.177-177
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• 2003

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.219-219
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• 2003

• Proceedings of the Korean Magnestics Society Conference
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• 2004.12a
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• pp.202-203
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• 2004