Magnetoresistance in Pd–Co/Cu/Pd–Co trilayer under hydrogen–nitrogen gas mixture

The magnetoresistance of three Pd–Co(1)/Cu/Pd–Co(3) trilayers with different Pd–Co(3) thicknesses were evaluated in a H2–N2 gas mixture. The resistance of Pd–Co/Cu/Pd–Co increased with increasing hydrogen concentration in the gas phase, which is similar to the behavior observed in the Pd metal. The peak structure was shown in the magnetoresistance under a nitrogen atmosphere and was associated with magnetic scattering at the interface between the Pd–Co and Cu layers. In the H2–N2 gas mixture, the peak position and width in the resistance profiles were independent of the hydrogen concentration for all the prepared trilayers, and the peak intensity decreased with increasing hydrogen concentration for the trilayer containing a 4.2 nm thick Pd–Co(3) layer. The decrease in intensity was due to the reduction in magnetization in the Pd–Co layer after hydrogen absorption. The change in the resistance ratio by hydrogen absorption in the trilayer was larger under a high external magnetic field of 170 mT than under a low magnetic field of 10 mT. These results confirmed that the multilayered structure of the Pd–Co/Cu enhances the resistance response to hydrogen under a high magnetic field.