Magnetic multilayers [Fe(20 A)/Pd(x A)]2, grown by electron-beam evaporation in high vacuum were studied by x-ray-diffraction, superconducting quantum interference device, vibrating-samplemagnetometer, magnetoresistance, and conversion-electron-Mossbauer-spectra measurements.From xray-diffraction measurements a structure transition of Fe layers from bcc to fcc was observed if the 0 thickness of Pd layers was over 36 A. An oscillatory behavior of saturation magnetization per unit Fe 0 volume was found with increment of thickness of Pd layer in the range of 6 to 60 A. Conversionelectron-Mossbauer-spectra measurements proved that the moment of Fe atoms in Fe/Pd multilayers is almost the same as for a single Fe film and the oscillatory magnetization is caused by the magneticpolarization effect of the Pd layers. An antiferromagnetic coupling between the polarization moments in the Pd layer could clearly be observed in a special Pd thickness range, and it might make the magnetization oscillate with the Pd layer thickness. No antiferromagnetic coupling between two Fe layers and the giant magnetoresistance effect were observed. The relationship among structure, interlayer coupling, and the magnetic-polarization effect of Pd layers was discussed.In the last few years oscillatory interlayer exchange coupling has becotne one of the most discussed phenomena in layered magnetic structures. ' Griinberg et al. discussed experimental evidence for antiferromagnetic interlayer exchange coupling in Fe/Cr/Fe sandwiched structures, following the discovery by Parkin et al. that the interlayer exchange may oscillate between ferromagnetic and antiferromagnetic coupling as a function of the spacer material thickness in various multilayered systems.In the antiferromagnetic coupling multilayer systems, the giant magnetoresistance (CxMR) efFect exists generally. Parkin had found the oscillatory exchange coupling between two ferromagnetic layers was a general phenomenon in magnetic multilayers with nonmagnetic metals as spacer layers. But he had not found evidence of antiferromagnetic coupling through nearly ferromagnetic metals (Pd, Pt) in magnetic multilayers.Only Celinski and Heinrich, in Fe(001)/Pd(001)/Fe(001) structures, observed a very weak antiferromagnetic coupling between Fe layers for a 12-ML-thick Pd layer. No antiferromagnetic coupling between ferromagnetic layers through Pt spacers and in other magnetic multilayered structures spaced with Pd layers, such as Co/Pd, Fe/Pt, and Co/Pt, was found. On the other hand, the magnetic polarization effect of Pd and Pt layers in multilayers had been observed. ' ' All the above seems to suggest that the spin-polarization effect of the Pd, Pt spacer layers have a great influence on the exchange coupling between two ferromagnetic layers and the MR effect in these systems.In this paper, we investigated the magnetic polarization effect of Pd layers in Fe/Pd multilayers and its influence on the exchange coupling between Fe layers through Pd

FdPd multilayers with different thichesses of Pd layers prepared by e-beam evaporation have been studied by 57Fe conversion electrbn Mtissbauer spectroscopy (CEMS) andx-ray diffraction (m). A structural transition of Fe layers from BCC to FCC in FdPd multilayers was found with the thickness of Pd layers dpd 2 36 A. The CEMS measurements indicated that the hyperline field Hw of the inner pans of the Fe layers was almost the same as that of B single-layer Fe film and HM of the interface Fe was enhanced slightly from that of a singlelayer Fe film. The moments of Fe layers were independent of the thickness of Pd layers and the structure of Fe layers, which suggmed that the FCC Fe had the same magnetic moment as BCC Fe i! W p d multilayers. The isomer shifts and quadrupole splitting increased abruptly for dw 2 36 A. This would correlate with the slructural transition of the Fe layers in F e d multilayers.

The magnetic properties of [Fe(20 Å)/Pd(x Å)]25 multilayers prepared by ultrahigh vacuum electron-beam evaporation are presented. It is found that the crystal structure of Fe layers change from bcc to fcc when the thickness of Pd layers dPd≥36 Å. The saturation magnetization per unit Fe volume at 5 K is enhanced and oscillates with the increment of the thickness of Pd layers, due to the polarization of Pd atoms. The magnetic hysteresis loops of samples indicate low coercive forces, and ferromagnetic coupling between the Fe layers for all Pd thicknesses (6–60 Å). The conversion electron Mössbauer spectra measurements proved that the magnetic moment of fcc Fe is the same as that of the bcc Fe. It is also found that the magnetic anisotropy dependence on dPd is similar to that of the saturation magnetization, and relates to the Fe layer structure transition. The Curie temperature of Fe/Pd multilayers decreases monotonously with the increasing of dPd. The low temperature magnetization measurement of Fe/Pd multilayers suggests that the interlayer coupling between Fe layers and polarization of Pd layers influences the temperature dependence of saturation magnetization. No evidence of antiferromagnetic coupling between Fe layers and giant magnetoresistance effect is found. The relationship among structure, polarization of Pd layers, and magnetic coupling is discussed.