No abstract

Metastable face-centered cubic (fcc) Fe/Cu(100) thin films are good candidates for ion-beam magnetic patterning due to their magnetic transformation upon ion-beam irradiation. However, pure fcc Fe films undergo spontaneous transformation when their thickness exceeds 10 ML. This limit can be extended to approximately 22 ML by deposition of Fe at increased CO background pressures. We show that much thicker films can be grown by alloying with Ni for stabilizing the fcc γ phase. The amount of Ni necessary to stabilize nonmagnetic, transformable fcc Fe films in dependence on the residual background pressure during the deposition is determined and a phase diagram revealing the transformable region is presented.

Metastable paramagnetic face-centered cubic (fcc) Fe films grown on a Cu(100) single crystal at room temperature can be transformed to the ferromagnetic body-centered cubic (bcc) structure by ion irradiation. We have employed this technique to write small ferromagnetic patches by Ar þ irradiation through a gold coated SiN mask with regularly arranged 80-nm diameter holes, which was placed on top of the as-prepared fcc Fe films. Nanopatterning was performed on both 8-monolayer (ML) Fe films grown in ultrahigh vacuum as well as 22-ML films stabilized by dosing carbon monoxide during growth. The structural transformation of these nano-patterned films was investigated using scanning tunneling microscopy. In both 8 and 22-ML fcc Fe films, the bcc needles are found to protrude laterally out of the irradiated part of the sample, limiting the resolution of the technique to a few 10 nm. The magnetic transformation was confirmed by magnetic force microscopy.

We have investigated the initial oxidation of the Rh(113) and Rh( 223) vicinal surfaces by STM and ab initio simulations. Upon adsorption of small amounts of oxygen, the surface morphology is completely altered. Surprisingly, oxygen-stabilized Rh adatoms can be observed on the (113) facets, with oxide-like electronic properties. We present models of these "0D oxide" phases and discuss reasons for their stability.