INFRARED-SPECTRA OF GIANT MAGNETORESISTANCE FE CR/FE TRILAYERS/

Magnetic-field-induced changes in infrared transmission and reflection from Fe/Cr/Fe trilayers are reported; Changes as large as approximate to 1% (compared with 4-5 % changes in resistivity) are observed aroun d 2000 cm(-1), and the magnitude of the effect decreases monotonically to zero at approximate to 5000 cm(-1). The field dependence mimics th at of the resistivity, and saturates at the same field at which the ma gnetization of the two Fe layers align parallel to each other. A simpl e model, which estimates the frequency dependence of the resistivity a nd includes the frequency dependence of the skin depth, produces semiq uantitative agreement with experiment.