Surface structure of CO on Co∕Pd(111) magnetic thin films and its effect on the spin reorientation transition of the film

Abstract

The CO surface structures on Co/ Pd͑111͒ magnetic thin film and the chemisorption-driven spin reorientation transition have been studied by soft x-ray spectroscopies. C 1s photoelectron diffraction for CO/ Co/ Pd͑111͒ revealed that CO is adsorbed both on the atop and bridge sites at 200 K, while CO is adsorbed exclusively on the atop site at 300 K. From simultaneous measurement of C 1s photoelectron spectroscopy and Co L-edge x-ray magnetic circular dichroism during stepwise CO adsorption and annealing, it was concluded that the spin reorientation transition is induced not by a thermodynamical effect but by the CO adsorption on the bridge site. These results show that the adsorption structure has a significant effect on the surface magnetic anisotropy of the thin film.

Density-functional study of the CO adsorption on ferromagnetic Co(0001) and Co(111) surfaces

“…The results for the fcc Co(1 1 1) surface are almost the same; an exception is somewhat higher m's for three-fold adsorption sites on Co(1 1 1) than on Co(0 0 0 1). The calculated C-O bond length for CO in the atop position agrees with the LEED result for the Co(0 0 0 1) surface [18], whereas we get slightly shorter Co-C separation than the value 1.78 ± 0.06 Å derived for adsorption above the (0 0 0 1) [18] and (1 1 1) [24] surface, respectively. According to the experiment [20], K co-adsorption moves CO to three-fold fcc and hcp sites above Co(0 0 0 1).…”

“…It would be interesting to know whether the latter result has some relation to the large Co-C distance for the CO in bridge position above Co(1 1 1) claimed for the lowtemperature chemisorption phase in the Ref. [24].…”

“…For higher CO coverage, new adsorption sites become occupied and complicated overlayer phases are formed [17,18,21], geometry of which is not completely clarified. In the realm of thin-film magnetism, the CO adsorption on Co (especially in Co (1 1 1)) is of special interest because of its ability to switch the magnetization orientation [22][23][24]. The conclusions arrived at in the last cited study are especially involved since they relate the spin reorientation to the presence/absence of weakly adsorbed CO in the bridge position.…”

Magnetic Patterning by Electron Beam-Assisted Carbon Lithography

“…In-plane to out-of-plane and out-of-plane to in-plane SRTs were observed for hcp Co/Ru(0001), occurring at thicknesses of 2 and 3 atomic layers (ALs), respectively . Further, we note that the MA of ultrathin Co films is known to be strongly influenced by the adsorption of CO and other gases, as has been repeatedly reported. − The choice of a heavy metal substrate, Re, was functional to obtaining strong and asymmetric exchange interactions at the interface, also known as the Dzyaloshinskii–Moriya interaction (DMI). , …”

Density-functional study of the CO adsorption on the ferromagnetic fcc Co(001) film surface

“…It has appeared that the results resemble those for chemisorption on the Co(0 0 0 1) surface -a conclusion that is quite natural because of the close similarity of the two surfaces. CO chemisorption on Co(1 1 1) films deposited on Pd(1 1 1) is of considerable interest [5] because of changing the film magnetization direction. The likeness does not extend to the film magnetic anisotropy because of the considerable anisotropy of the bulk region [6] in hcp films.…”