L.C.C.M. Nagamine

Effect of interface intermixing on giant magnetoresistance in NiFe/Cu and Co/NiFe/Co/Cu multilayers

This article reports on the important influence of the spontaneously built-in paramagnetic interfacial layers on the magnetic and magnetoresistive properties of NiFe/Cu and Co/NiFe/Co/Cu multilayers grown by magnetron sputtering. A computational simulation, based on a semiclassical model, has been used to reproduce the variations of the resistivity and of the magnetoresistance (MR) amplitude with the thickness of the NiFe, Cu, and Co layers. We showed that the compositionally intermixed layers at NiFe/Cu interfaces, which are paramagnetic, reduce the flow of polarized electrons and produce a masking on the estimated mean-free path of both types of electrons due to the reduction of their effective values, mainly for small NiFe thickness. Moreover, the transmission coefficients for the electrons decrease when Fe buffer layers are replaced by NiFe ones. This result is interpreted in terms of the variations of the interfacial intermixing and roughness at the interfaces, leading to an increase of the paramagnetic interfacial layer thickness. The effect provoked by Co deposition at the NiFe 16 A/Cu interfaces has also been investigated. The maximum of the MR amplitudes was found at 5 A of Co, resulting in the quadruplication of the MR amplitude. This result is partially attributed to the interfacial spin-dependent scattering due to the increase of the magnetic order at interfaces. Another effect observed here was the increase of the spin-dependent scattering events in the bulk NiFe due to a larger effective NiFe thickness, since the paramagnetic interfacial layer thickness is decreased.This article reports on the important influence of the spontaneously built-in paramagnetic interfacial layers on the magnetic and magnetoresistive properties of NiFe/Cu and Co/NiFe/Co/Cu multilayers grown by magnetron sputtering. A computational simulation, based on a semiclassical model, has been used to reproduce the variations of the resistivity and of the magnetoresistance (MR) amplitude with the thickness of the NiFe, Cu, and Co layers. We showed that the compositionally intermixed layers at NiFe/Cu interfaces, which are paramagnetic, reduce the flow of polarized electrons and produce a masking on the estimated mean-free path of both types of electrons due to the reduction of their effective values, mainly for small NiFe thickness. Moreover, the transmission coefficients for the electrons decrease when Fe buffer layers are replaced by NiFe ones. This result is interpreted in terms of the variations of the interfacial intermixing and roughness at the interfaces, leading to an increase of the paramagne...

Cone magnetization state and exchange bias in IrMn∕Cu∕[Co∕Pt]3 multilayers

The effects of a Cu interlayer on the perpendicular exchange bias in IrMn∕Cu∕[Co∕Pt]3 multilayers were investigated by focusing on the correlation between the exchange bias and the magnetic anisotropy. The in-plane magnetization hysteresis loops were interpreted in the framework of a phenomenological model based on the coherent magnetization rotation, indicating that the easy magnetization axis makes an angle of approximately 15° with the normal of the IrMn∕[Co∕Pt]3 film. This angle decreases with the introduction of the Cu spacer thickness in the IrMn∕Cu∕[Co∕Pt]3 system, indicating that the Cu interlayer leads to a predominant perpendicular anisotropy. Although a maximum of the out-of-plane anisotropy is found for Cu layer thickness between 4 and 5A, the maximum of the perpendicular exchange bias was found at 3A of Cu, which could be attributed to the interplay between two effects, mainly the increase in the effective perpendicular anisotropy with the Cu spacer thickness due to the reorientation of the C...