• Title/Summary/Keyword: spin valve structure

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Anomalous Exchange Bias of the Top and Bottom NiFe Layers in NiFe/FeMn/NiFe Based Spin Valve Multilayers (NiFe/FeMn/NiFe 스핀밸브 구조의 다층박막에서 상 하부 NiFe 두께에 따른 교환바이어스 조사)

  • S.M. Yoon;J.J. Lim;V.K. Sankar;Kim, C.G.;Kim, C.O.
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2003.11a
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    • pp.212-212
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    • 2003

  • Many of the spin valve multilayer structures with FeMn as antiferromagnetic layer consist of a NiFe/FeMn/NiFe trilayer where the bottom NiFe layer is the seed layer to facilitate the growth of (111) gama-FeMn antiferromagnetic phase and the top NiFe layer forms the pinned layer[1], In this study, exchange bias of bottom NiFe layer has been investigated as functions of thicknesses of top and bottom NiFe in NiFe/FeMn/NiFe, prepared by rf magnetron sputtering, MH-loop was measured by vibration sample magnetometer (VSM). Two hysteresis loops are corresponded to bottom and top layers, similar to reported loops in spin valve structure. Exchange bias of bottom NiFe could be induced by the interfacial coupling between bottom NiFe and FeMn. But those coupling are strongly dependent on the top and bottom NiFe thicknesses, revealing anomalous character ul exchange bias of bottom NiFe layer.

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The Second Annealing Effect on Giant Magnetoresistance Properties of PtMn Based Spin Valve (이차 열처리가 PtMn계 스핀밸브의 거대자기저항 특성에 미치는 영향)

  • 김광윤;김민정;김희중
    • Journal of the Korean Magnetics Society
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    • v.11 no.2
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    • pp.72-77
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    • 2001

  • Top spin valve films with PtMn antiferromagnetic layers were deposited using a multi-target dc magnetron sputtering in (100)Si substrates overcoated with 500 $\AA$ of Al$_2$O$_3$. Firstly, the post-deposition annealing was performed at 270$\^{C}$ in a unidirectional magnetic field of 3 kOe to induce the crystallographic transformation of the PtMn layer from a fcc (111) to a fct (111) structure. Secondly, the spin valve films were annealed without magnetic fields and magnetic properties were measured. In Si/A1$_2$O$_3$ (500$\AA$)/Ta(50$\AA$)NiFe(40$\AA$)/CoFe(17$\AA$)/Cu(28$\AA$)/CoFe (30$\AA$)PtMn(200$\AA$)Ta(50$\AA$) top spin valve samples, the MR ratio decreased slowly with increasing annealing temperature up to 325$\^{C}$. But above 325$\^{C}$, the MR ratio decreased rapidly to 1%, due to a collapse of the exchange coupling between a antiferromagnetic layer and a pinned layer with increasing annealing temperature. Also above 325$\^{C}$, the exchange biased field rapidly decreased and the interlayer coupling field rapidly increased with increasing annealing temperature. A change in the interlayer coupling field was resulted from the increase in interface roughness due to Mn-interdiffusion through the grain boundaries. We confirmed the temperature in changing magnetic properties agreed well with the blocking temperature of PtMn based spin valve structure.

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