Oxygen as a surfactant in the growth of giant magnetoresistance spin valves

Egelhoff, William F.; Chen, P. J.; Powell, Cedric J.; Stiles, Mark D.; McMichael, Robert D.; Judy, J.; Takano, K.; Berkowitz, A. E.

doi:10.1063/1.365620

Cited by 197 publications

(56 citation statements)

References 24 publications

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“…The calculations were performed assuming a bulk scattering with γ = 0.7eV that gives a saturation resistivity of 23µΩcm and a GMR of 16% in agreement with experimental data by Egelhoff et al 91,93 As is seen from Fig.34a, for the parallel (P) configuration the local conductivity of the Co layers is much higher for the majority spins than for the minority spins, which reflects the spin-dependent conductivity in the bulk Co (see Fig.31b at E=E F ). The local conductivities σ Cu in the Cu layers are higher than those in the Co layers and are different for different spins.…”

mentioning

confidence: 96%

“…Specular scattering of electrons at Co/CoO interfaces was also suggested to be the reason for the enhancement of GMR by up to 17% at room temperature, obtained in bottom spin valves of the type NiO/Co/Cu/Co, in which the top Co layer was slightly oxidized. 91,90 Sugita et al 92 regarded the high magnitude of GMR of 28% obtained in an epitaxially-grown symmetric spin valve with an α- The importance of overlayers deposited at the top outer boundary of the NiO/Co/Cu/Co spin valve was demonstrated by Egelhoff et al 93 They found that the deposition of about 2 monolayers (ML) of Au, Ag, or Cu increases GMR, whereas the deposition of 2ML of Ta, Si, C, or Ni 80 Fe 20 decreases GMR. These results were interpreted by Egelhoff et al as evidence of enhanced specular scattering for the case of Au, Ag, and Cu, but suppressed specular scattering for the case of Ta, Si, C, and Ni 80 Fe 20 at the interface with Co.…”

Section: Outer Boundary Dependencementioning

confidence: 99%

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Perspectives of giant magnetoresistance

Tsymbal¹,

Pettifor²

2001

Solid State Physics

252

189

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mentioning

confidence: 96%

Section: Outer Boundary Dependencementioning

confidence: 99%

Perspectives of giant magnetoresistance

Tsymbal¹,

Pettifor²

2001

Solid State Physics

252

189

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“…The latter routine takes advantage of introduced vacuum interfaces, since the slowly growing film surface remains in the process atmosphere for the time of rotation until it passes the open shutter again. During this time, remnant gases adsorb at the surface and act as a surfactant during the sputter process, which leads to smoother film surfaces and thus higher interface qualities in multilayer systems 164,165 . Furthermore, it results in a more homogeneous film thickness across the substrate area by eliminating the deposition rate variation in the tangential direction of the carousel rotation, which is beneficial for larger sample sizes or arrays.…”

Section: Magnetic Thin Film Depositionmentioning

confidence: 99%

Stretchable Magnetoelectronics

et al. 2011

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Abstract:In this work, stretchable magnetic sensorics is successfully established by combining metallic thin films revealing a giant magnetoresistance effect with elastomeric materials. Stretchability of the magnetic nanomembranes is achieved by specific morphologic features (e.g. wrinkles), which accommodate the applied tensile deformation while maintaining the electrical and magnetic integrity of the sensor device. The entire development, from the demonstration of the world-wide first elastically stretchable magnetic sensor to the realization of a technology platform for robust, ready-touse elastic magnetoelectronics with fully strain invariant properties, is described. The prepared soft giant magnetoresistive devices exhibit the same sensing performance as on conventional rigid supports, but can be stretched uniaxially or biaxially reaching strains of up to 270% and endure over 1,000 stretching cycles without fatigue. The comprehensive magnetoelectrical characterization upon tensile deformation is correlated with in-depth structural investigations of the sensor morphology transitions during stretching.With their unique mechanical properties, the elastic magnetoresistive sensor elements readily conform to ubiquitous objects of arbitrary shapes including the human skin. This feature leads electronic skin systems beyond imitating the characteristics of its natural archetype and extends their cognition to static and dynamic magnetic fields that by no means can be perceived by human beings naturally.Various application fields of stretchable magnetoelectronics are proposed and realized throughout this work. The developed sensor platform can equip soft electronic systems with navigation, orientation, motion tracking and touchless control capabilities. A variety of novel technologies, like smart textiles, soft robotics and actuators, active medical implants and soft consumer electronics will benefit from these new magnetic functionalities. Michael Melzer: Stretchable MagnetoelectronicsOutline 4

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“…One of the promising ways to increase the giant magnetoresistance (GMR) is the use of specular reflection layers such as nano-oxide layers (NOLs) [1][2]. Although NOLs play an important role to enhance GMR effect in specular spin valves, the process control of the NOLs still remains a challenge for the applications in disk drives.…”

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confidence: 99%

Structural Characterization of Nano-Oxide Layers in PtMn Based Specular Spin Valve Thin Films

Chen

2005

MAM

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In order to meet the requirements of magnetic read heads for higher density recording, a larger magnetoresistance for current spin valves is needed. One of the promising ways to increase the giant magnetoresistance (GMR) is the use of specular reflection layers such as nano-oxide layers (NOLs) [1][2]. Although NOLs play an important role to enhance GMR effect in specular spin valves, the process control of the NOLs still remains a challenge for the applications in disk drives. The relationship between NOL structure and magnetic correlation is still not fully understood so far [3]. Therefore, it is necessary to understand the structural charactorization of NOLs in spin valves at atomic level.The PtMn based specular spin valve structures studied in this paper are Ta/NiFeCr/PtMn/ CoFe/Ru/CoFe/NOL/CoFe/Cu/CoFe/NiFe/Cu/Ta-O. All samples were deposited with magnetron sputtering and annealed at 230-300 o C under an in-plane magnetic field in a vacuum furnace for 8-10 hours. The NOLs at pinned layer side were fabricated by oxidizing CoFe synthetic pinned layer CoFe/Ru/CoFe/NOL/CoFe with natural and plasma oxidation. The oxygen exposure was controlled to be below 10 mT·sec in both oxidation processes. A systematic structure characterization of nanooxide layers and specular spin valves by using high-resolution transmission electron microscopy (HRTEM) has been studied. Figure 1 and 2 show that the specular reflection effect from the NOLs was found to enhance GMR ratio from 12% in the spin valve with no NOL to more than 15% and 16% in the case of natural and plasma oxidation of the NOL, an increase in GMR ratio by more than 30%. Oxygen exposure plays an important role in NOLs process. HRTEM reveals that oxide clusters mixing with insufficiently oxidized CoFe layers prevailed in natural NOL, and the natural oxidation was inhomogeneous, as shown in Figure 3. In contrast, plasma NOL has a thinner, more homogeneously oxidized CoFe layers with sharp interfaces, as shown in Figure 4. In plasma NOLs, the structures still maintain CoFe crystal structure. This comparison indicates that plasma oxidation is much better than natural oxidation to create desirable NOLs. A large GMR ratio can be obtained in NOL specular spin valves by plasma oxidation process. Fabricating NOLs without any degradation in crystal structure is critical to obtain high GMR ratio. In plasma NOLs, CoFe fcc crystal structure with minimum crystal degradation have been achieved. References[1] W.

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Oxygen as a surfactant in the growth of giant magnetoresistance spin valves

Cited by 197 publications

References 24 publications

Perspectives of giant magnetoresistance

Perspectives of giant magnetoresistance

Stretchable Magnetoelectronics

Structural Characterization of Nano-Oxide Layers in PtMn Based Specular Spin Valve Thin Films

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