• Journal of Magnetics
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• v.13 no.2
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• pp.43-52
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• 2008

The objective of this paper is to review the magnetic and magneto-transport properties of Co/$Co_2TiSn$ consisting of two metallic magnetic phases that are antiferromagnetically exchange-coupled at the phase boundary. The bulk Co/$Co_2TiSn$ system, which has a $Co_2$TiSn Heusler alloy precipitates in the hexagonal Co matrix, showed an unusual coercivity change with a concurrent change in temperature, and was modeled on the basis of a wall formation caused by exchange coupling at the phase boundary. For measurements of magneto-transport properties, Co/$Co_2TiSn$ thin films that had two-magnet phases were deposited using a magnetron sputtering system with a composite target. The magnetization process in the films is also explained on the basis of the model of wall formation at the phase boundary. Annealed Co/$Co_2TiSn$ films showed a 0.12% GMR effect, indicating the scattering of polarized conduction electrons due to the antiparallel exchange coupling at the phase boundary. The scattering process of conduction electrons at the phase boundary was modeled with relation to the magnetization process.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.679-682
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• 1995

The observed high-field magnetization curves of $Sm_{2}Fe_{17}N_{3.0}$ at 4.2 K and 296 K are well reproduced by the calculation using the Sm-Fe exchange field $2\mu\textrm{B}H_{ex}\;=\;320\;K$ and two crystalline electric field parameters ${A_{0}}^{2}=\;-910\;K$ and ${A_{1}}^{0}=\;200\;K$. The calculation shows that during the magnetization process along the hard axis at 4.2 K, the Sm moment rotates toward the direction antiparallel to H when H < 110 kOe and then returns to the field direction with further increase of the field. At 296 K, the Sm moment rotates toward the direction antiparallel to H monotonously with increasing field and finally becomes antiparallel to H when $H{\geq}H_{A}=210\;kOe$. The particular magnetization process of the Sm moment can be explained by the field-induced noncollinear coupling between the spin and orbital moments of the Sm ion.

• 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.13 no.1
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• pp.11-18
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• 2008

This study examines a new macroscopic ferrimagnet, Co-TbN. This ferrimagnet, consisting of two metallic phases, Co and TbN, demonstrated the typical macroscopic ferrimagnet properties of a magnetic compensation point and a negative giant magnetoresistance (GMR). The Co-TbN system with 32% TbN composition showed 0.72% GMR in magnetic fields up to 8 kOe at room temperature and 9% GMR in 40 kOe at 250 K. In the Co-TbN system, GMR exhibited a different dependence on temperature from that of ordinary GMR materials whose negative magnetoresistance decreases with increasing temperature. In contrast to ordinary GMR materials whose negative magnetoresistance decreases with increasing temperature, the GMR effect in the Co-TbN system increased with increasing temperature, due to the increase of ferromagnetic alignment of the Co and TbN in the magnetic field caused by the decreased exchange coupling with increasing temperature.

• Journal of Magnetics
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• v.6 no.4
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• pp.132-141
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• 2001

The switching characteristics and the magnetization-flop behavior in magnetic tunnel junctions exchange biased by synthetic antiferromagnets (SyAFs) are investigated by using a computer simulations based on a single-domain multilayer model. The bias field acting on the free layer is found to be sensitive to the thickness of neighboring layers, and the thickness dependence of the bias field is greater at smaller cell dimensions due to larger magnetostatic interactions. The resistance to magnetization flop increases with decreasing cell size due to increased shape anisotropy. When the cell dimensions are small and the synthetic antiferromagnet is weakly, or not pinned, the magnetization directions of the two layers sandwiching the insulating layer are aligned antiparallel due to a strong magnetostatic interaction, resulting in an abnormal magneto resistance (MR) change from the high-MR state to zero, irrespective of the direction of the free-layer switching. The threshold field for magnetization-flop is found to increase linearly with increasing antiferromagnetic exchange coupling in the synthetic antiferromagnet. Irrespective of the magnetic parameters and cell sizes, magnetization flop does not exist near zero applied field, indicating that magnetization flop is driven by the Zeeman energy.

• Journal of Magnetics
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• v.6 no.3
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• pp.83-85
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• 2001

The magnetoresistance properties of NiO/NiFe/Cu/NiFe spin valve film deposited on MgO(100) substrate with YBa$_2$$Cu_3O_7$(YBCO) film were investigated at room temperature and at 77 K. The magnetoresistance (MR) curves of the hybrid superconductor-magnetoresistor film structure showed an exchange coupling field of 300 Oe and an inverse magnetoresistance ratio of -6.5%. The magnetization configurations of the two magnetic layers in the NiO spin valve were antiparallel due to an increment in the conduction electron flow to superconductor YBCO film. This sample showed an inverse MR ratio.

• Journal of the Korean Magnetics Society
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• v.11 no.3
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• pp.85-96
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• 2001

Experimental magnetization-temperature curves for melt-spun ribbons of amorphous alloys (Dy$\_$0.33/Fe$\_$0.67/)$\_$1-x/B$\_$x/(x=0 ,0.05, 0.1, and 0.15) and (Sm$\_$0.33/Fe$\_$0.67/)$\_$1-x/B$\_$x/(x=0, 0.01, 0.02, and 0.03) (in atomic fraction) are fitted with theoretical equations based on the mean field theory in order to calculate exchange couplings between constituent elements as a function of the B content. In the case of the DyFe$_2$-B system, the sign of the exchange coupling between Dy and Fe is negative, indicating that the magnetization direction of Dy is antiparallel to that of Fe. The sign of the other two couplings are positive indicating a parallel alignment. The exchange coupling between Fe ions are greatest, while that between Dy ions is negligible. In the case of the SmFe$_2$B alloys, the sign of all the couplings are positive, indicating ferromagnetic coupling between the spins. The exchange couplings between Fe ions, and Fe and Sm are comparable to each other, but they are much greater than that between Sm ions. The high exchange coupling between Fe and Sm, which is considered to occur indirectly, is rather unexpected, but it is considered to be unique characteristics of amorphous Sm-Fe alloys. In both alloy systems, the exchange coupling between Fe ions increases with increasing B content. and this may be explained by the increase of the Fe-Fe separation with increasing B content. The exchange coupling between Fe and RE also increases with increasing B content. As the B content increases, the magnetization decreases over the whole temperature range, and the Curie temperature also decreases.

• Journal of the Korean Magnetics Society
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• v.27 no.4
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• pp.115-122
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• 2017

The antiferromagnet IrMn based four different GMR-SV multilayers on Corning glass were prepared by using ion beam deposition and DC magnetron sputtering system. The magnetoresistance (MR) properties for single-type and dual-type GMR-SV multilayer films were investigated through the measured major and minor MR curves. The exchange bias coupling field ($H_{ex}$) and coercivity ($H_c$) of pinned layer, the $H_c$ and interlayer exchange coupling field ($H_{int}$) of free layer for the dual-type structure GMR-SV multilayer films consisted of top IrMn layer were 410 Oe, 60 Oe, 1.6 Oe, and 7.0 Oe, respectively. The minor MR curve of two free layers was performed the squarelike feature having a MR ratio of 8.7 % as the sum of 3.7 % and 5.0 %. The value of average magnetic field sensitivity (MS) was maintained at 2.0 %/Oe. Also, the magnetoresistance properties of the single-type and dual-type structure GMR-SV multilayer films consisted of bottom IrMn layer were decreased more than those of top IrMn layer. Two antiparallel states of magnetization spin arrays of the pinned and free layers in the dual-type GMR-SV multilayer films occurred the maximum MR value by the effect of spin dependence scattering.