Study of Giant Magnetoresistance in Ferrimagnetic Multilayer Films

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1. magnetic and magnetotransport properties of Fe/Gd multilayers prepared by rf sputtering have extensively investigated. Fe/Gd multilayers have been found to behave as 'giant' ferrimagnets, that is, the magnetizations of Fe and Gd layers couple in antiparallel due to the antiferromagnetic exchange interaction at the interfaces. In the present study, spin-flop and compensation phenomena of the magnetization in Fe/Gd multilayers were observed. it was also revealed that a crossover between the longitudinal and transverse magnetoresistances occurred accompanied with the spin-flop of magnetization.2. The magnetization vs. field and vs. temperature curves in Fe/Gd multilayers were calculated using the magnetic structure predicted by the molecular field theory. The systematic comparison between the experiments and the calculations has been made. The calculated results agree fairly well with the experiments, suggesting-that the molecular field theory is useful for the prediction of the magnet … More ic structure in ferrimagnetic multilayers. The crossover of magnetoresistances was reproduced qualitatively well by the calculation on the assumption that the current flew in parallel in each atomic layer. This indicates that the crossover occurs due to the change in the magnetic structure around the spin-flop field.3. From the application point of view, it is necessary to obtain the spin-flop of magnetization and the crossover of magnetoresistances at room temperature and in low fields. We prepared Fe/Gd double structured multilayers, where the two different Fe/Gd submultilayers with a short period lambda_s were stacked alternately with a long period lambda_1. The lambda_s and lambda_1 dependences of the spin-flop field has been investigated. It has been found that the spin-flop occurs at room temperature and in a field lower than 1000e by choosing lambda_s where the compensation temperature approaches room temperature and/or by choosing large lambda_1.4. The fundamental study of giant magnetoresistance in Fe/Cr multilayers has also been made. Less