Spin-resolved photoemission of in-situ sputtered iron and iron-yttrium alloys

Spin-resolved photoemission spectra of amorphous Fe-Y alloys have been obtained and compared with both those of pure Fe and with theoretical electronic structure calculations. The thin iron and alloy films were prepared by in situ sputtering, and the spectra were obtained using 110-eV photons from the UK Synchrotron Facility. From secondary electron spin hysteresis loops, Fe60Y40 starts to order ferromagnetically well before the lowest temperature accessible with our equipment (114 K), but Fe41Y59 shows no polarization down to this temperature. Although the spin-integrated photoemission spectrum of the valence band of Fe60Y40 shows little difference from that of pure Fe, the spin-resolved spectra are significantly different. Fe60Y40 also exhibits a reduced valence band polarization (14%) compared with iron, and contrary to predictions, the majority spin states of Fe60Y40 dominate at the Fermi edge. No evidence is found for strong ferromagnetism. Unexpectedly, the 1-eV secondary electron polarization of Fe60Y40 (7%) is found to be low compared with the valence band polarization, an effect that may be due to a negative moment on the yttrium. © 1997 The American Physical Societ

Remote two-dimensional imaging of giant magnetoresistance with spatial resolution

Spatially resolved two-dimensional images of giant magnetoresistance (GMR) are demonstrated in Co/Cu and CoFe/Cu multilayers by remote imaging of the sample temperature using an infrared charge coupled device camera. We have previously shown that the emissivity of a giant magnetoresistive material at infrared wavelengths is related to its electrical resistance [S. M. Stirk et al., Appl. Phys. Lett. 86, 102505 (2005)]. Here, the change in emissivity in an applied magnetic field is sensed by the camera as a field dependent temperature image. Using the inherent spatial resolution of the camera, we characterize the GMR on a spatial scale of 200 microns across the sample surface. In a small sputtered Co/Cu multilayer sample, a significant variation of the GMR over the sample surface is observed, a characteristic previously undetectable by conventional electrical measurements. By contrast, no such spatial variation of the GMR is observed from a commercially grown CoFe/Cu wafer. These measurements demonstrate the potential for quick and remote imaging of magnetoresistance with spatial resolution with possible applications such as the whole wafer characterization of GMR materials and the magnetoresistance in patterned arrays