B. Reuscher

Magnetic patterning of Fe∕Cr∕Fe(001) trilayers by Ga+ ion irradiation

Magnetic patterning of antiferromagnetically coupled epitaxial Fe(10nm)∕Cr(0.7nm)∕Fe(10nm)(001) trilayers by irradiation with 30keV Ga+ ions was studied by means of atomic force microscopy, magnetic force microscopy, and Kerr magnetometry. It was found that within a fluence range of (1.25−5)×1016ions∕cm2 a complete transition from antiferromagnetic to ferromagnetic coupling between the two Fe layers can be achieved. The magnetization reversal processes of the nonirradiated, antiferromagnetically coupled areas situated close to the irradiated areas were studied with lateral resolution. Evidence for a lateral coupling mechanism between the magnetic moments of the irradiated and nonirradiated areas was found. Special attention was paid to preserve the flatness of the irradiated samples. Depending on the fluence, topographic steps ranging from +1.5to−2nm between the nonirradiated and irradiated areas were observed. At lower fluences the irradiation causes an increase of the surface height, while for higher fl...

Analysis of the Crack Initiation at Non-Metallic Inclusions in High-Strength Steels

Abstract High-strength steels exhibit different fracture surface characteristics under cyclic load when failure is initiated by non-metallic inclusions depending on the lifespan. These can be attributed to different crack propagation mechanisms. These characteristics are correlated with the short and long crack propagation. As far as the short crack is concerned, the mechanism of the discontinous decohesion of carbides in the immediate vicinity of the inclusions and the merging of the resulting microcracks to form a macrocrack is discussed. This postulated mechanism is investigated by means of a combination of scanning electron microscope (SEM) analyses of the fracture surface and target preparation by means of focused ion beam (FIB) by a detailed resolution of the local microstructure around the crack-initiating inclusion and the crack path.

Fabricating high-density magnetic storage elements by low-dose ion beam irradiation

We fabricate magnetic storage elements by irradiating an antiferromagnetically coupled ferromagnetic/nonmagnetic/ferromagnetic trilayer by a low-dose ion beam. The irradiated areas become ferromagnetically coupled and are capable of storing information if their size is small enough. We employ Fe/Cr/Fe trilayers and a 30 keV focused Ga+-ion beam to demonstrate the working principle for a storage array with a bit density of 7  Gbit/in.2. Micromagnetic simulations suggest that bit densities of at least two magnitudes of order larger should be possible.