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

Abstract

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, ${\mathrm{Fe}}_{60}$${\mathrm{Y}}_{40}$ starts to order ferromagnetically well before the lowest temperature accessible with our equipment (114 K), but ${\mathrm{Fe}}_{41}$${\mathrm{Y}}_{59}$ shows no polarization down to this temperature. Although the spin-integrated photoemission spectrum of the valence band of ${\mathrm{Fe}}_{60}$${\mathrm{Y}}_{40}$ shows little difference from that of pure Fe, the spin-resolved spectra are significantly different. ${\mathrm{Fe}}_{60}$${\mathrm{Y}}_{40}$ also exhibits a reduced valence band polarization (14%) compared with iron, and contrary to predictions, the majority spin states of ${\mathrm{Fe}}_{60}$${\mathrm{Y}}_{40}$ dominate at the Fermi edge. No evidence is found for strong ferromagnetism. Unexpectedly, the 1-eV secondary electron polarization of ${\mathrm{Fe}}_{60}$${\mathrm{Y}}_{40}$ (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.