Induced exchange bias in NiMn/CoFe multilayer thin films sputtered on a quartz substrate by field cooling
Résumé
We demonstrated the influence of the annealing temperature, the thickness of CoFe &NiMn and the shape anisotropy of stripes on the macroscopic magnetization of theCoFe/NiMn multilayer sputtered on a quartz substrate. The annealing temperaturemakes the exchange bias field (Hex) appear for T > 200°C and allow an adequate shiftof the hysteresis loop for T ≈ 275°C. The thicknesses of CoFe and NiMn play on thestrength of the exchange bias, making it stronger when the thickness of CoFe is lowand when the thickness of NiMn is high. In consequence, the remanent magneticmoment in the easy axis , the proportion of remanent magnetic moment in the hardaxes and the variation of the magnetic moment in the easy axis around null fieldincrease when the exchange bias weakens. A process was successfully designed tocreate stripes out of the CoFe/NiMn multilayer. As it is, the introduced shapeanisotropy does not favour a direction for the global magnetization but attenuate a lotthe sensitivity of the magnetization to a magnetic field in the hard axis.
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