Magnetic properties and giant magnetoresistance effect in [Fe/Pt]n granular multilayers

We report in this paper the first observation of giant magnetoresistance as high as 23% in electrodeposited [Fe/Pt](n) granular multilayers with different thicknesses of bi-layers. [Fe/Pt](n) multilayers were prepared by electrodeposition, through the single bath technique. Cu (100) textured polycrystalline foils were used as substrate. The composition of the studied samples is Cu:Pt(x nm)/[Fe(t(Fe) nm)/Pt(x nm)](n), in which the thickness of the iron layer varied between 2.5+12.5 nnn while the thickness of the non-magnetic Pt layer is varied by changing the bottom Pt layer thickness x between 0.5+3.0 nm. The SEM characterization of the multilayer revealed a granular structure of the deposit with the granule diameter in the range from 2 to 11 nm. These results are comparable with those obtained by the X-ray diffraction measurements of crystallites size obtained by the Scherer equation. The hysteresis loops showed that the magnetic properties are influenced both by the thickness of the bi-layer and by the number of periods (n). The coercivity (H-c) varied in the range 8+21 kA.m(-1) and the remanence ratio was M/M-s = 0.23+0.81. The samples display out of plane anisotropy and anti-ferromagnetic type coupling between layers, as it was emphasized by means of the torsion magnetometer. [Fe/Pt] electrodeposited multilayers display giant magnetoresistance effect which can be explained mainly by the exchange interaction among neighbouring layers and by the spatially inhomogeneous magnetic structure of the granular multilayer (favouring spin scattering at the interfaces between grains and layers).