We investigated the magnetoresistance of La2/3Ca1/3MnO3+δ magnetic thin films. Under certain conditions, the magnetoresistance curves show a remarkable hysteresis and the resistance becomes dependent on the magnetic history. A relaxation behavior of the resistance has also been observed. Hysteresis and relaxation of the resistance are very similar to the phenomena of magnetoviscosity of the magnetic moment in spin glasses and the magnetic aftereffect in hard magnets.

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A novel granular multilayer structure consisting of magnetic granular AgCo layers and non-magnetic Cu spacer layers is introduced to study their magnetotransport properties. The results are similar to those obtained from both conventional multilayers and granular single-films, but with a notable enhancement of low-field sensitivity compared to these structures. This can be attributed to a weak antiferromagnetic coupling across the Cu spacer layer between interfacial Co particles. Direct evidence for this interlayer coupling is given by the observation of magnetoresistance oscillations with variation of the Cu spacer thickness. The oscillation period obtained here for Cu(111) spacer layers is close to 3 atomic layers.

Microstructural origin of giant magnetoresistance in a new sensor structure based on NiFe/Ag discontinuous multilayer thin films