Layer thickness and temperature variation of the giant magnetoresistance in Fe/Ag multilayers

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Abstract
The magnetoresistance ratio in Fe/Ag multilayers is increased dramatically with decreasing Fe layer thickness. This behavior can be explained in terms of interference of electronic Bloch waves due to interface roughness and lattice mismatch between Fe and Ag layers. At the same time, the interlayer coupling changes from ferromagnetic to antiferromagnetic when the Fe layer thickness is decreased. An anomalous temperature effect of magnetoresistance is also observed. The magnetoresistance ratio at 4.2 K is smaller than that at 300 K when the Fe layer thickness is larger than about 12 Å, which can be attributed to the presence of some superparamagnetic‐like thin pieces at the interfaces.