Surface atomic relaxation and magnetism on hydrogen-adsorbed Fe(110) surfaces from first principles

We have computed adsorption energies, vibrational frequencies, surface relaxation and buckling for hydrogen adsorbed on a body-centred-cubic Fe(110) surface as a function of the degree of H coverage. This adsorption system is important in a variety of technological processes such as the hydrogen embrittlement in ferritic steels, which motivated this work, and the Haber–Bosch process. We employed spin-polarised density functional theory to optimise geometries of a six-layer Fe slab, followed by frozen mode finite displacement phonon calculations to compute Fe–H vibrational frequencies. We have found that the quasi-threefold (3f) site is the most stable adsorption site, with adsorption energies of ∼3.0 eV/H for all coverages studied. The long-bridge (lb) site, which is close in energy to the 3f site, is actually a transition state leading to the stable 3f site. The calculated harmonic vibrational frequencies collectively span from 730 to 1220 cm−1, for a range of coverages. The increased first-to-second layer spacing in the presence of adsorbed hydrogen, and the pronounced buckling observed in the Fe surface layer, may facilitate the diffusion of hydrogen atoms into the bulk, and therefore impact the early stages of hydrogen embrittlement in steels

Zur Adsorption von Wasserstoff auf Metalloberflaechen. Eine Untersuchung am Beispiel von Eisen- und Rhodiumoberflaechen

SIGLEAvailable from TIB Hannover: DW 2810 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Charakterisierung von Struktur und Eigenschaften ferromagnetischer Schichten als Voraussetzung fuer die Optimierung und Weiterentwicklung von Systemen zur Datenaufzeichnung Abschlussbericht

SIGLEAvailable from TIB Hannover: F98B1284+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Charakterisierung dünner Ferromagneten mit Hilfe der Barkhausenrausch-Mikroskopie

Ferro-magnetic materials are extremely important in the recording of data and are manufactured in the form of thin coatings on data carriers or in the read-write heads of data storage instruments. The high storage capacities required can only be achieved providing that the coating system has homogeneous magnetic properties and low internal stresses. These properties can be achieved by the correct control of the processing parameters. Barkhausen noise microscopy offers the possibility of characterising such thin coatings at high resolution in terms of their structure, thickness, internal stresses and heat treated condition. The monstrated with reference to Sendust-coatings and coating systems for MR-sensors

Nondestructive techniques for a high resolution characterization of materials

Microsystem technology is qualitative challenge in the field of nondestructive testing. On the one side, this is due to the size of the specimens and on the other side, to the large quantity of the components to be tested. Since in many cases the testing speed does not correlate to these demands, the focal point of the application of nondestructive testing in microsystem technologies lies in the field of material and technology development. Because of the increase of the resolution capacity of nondestructive methods and the miniaturization of the sensors, resolutions in the micrometer range can be obtained which are demanded by microsystem technology. This paper tries to give a global view of potentials of different nondestructive high resoultion testing methods for the ndt characterization of materials in microsystem technology and tries to show possible tendencies in development