Thin films and surface magnetic

M. P. is particularly grateful to Prof Ulrich Gradmann who introduced him to thin film and surface magnetism and focused his interest on the subject for the succeeding years. 

Experimental geometry used in nuclear resonant scattering of synchrotron radiation from thin films and surfaces. 0 and 0 define the relative orientation of the incident wave vector Ar to the direction of a unidirectional magnetization m of the sample, a and n are the linear polarization basis vectors, and

incidence angle. (Reproduced from Ref. 22 with permission of Springer.)... 

Figure 1.7 sketches the grazing incidence scattering geometry used for studies of thin films and surfaces. The set of polarization vectors (cr, n), the polar and azimuthal angles (0, ) describing the relative orientation of the v/ave vector ko of the incident photons to the direction of the magnetization vector m of the sample are indicated. 

The Stoner criterion provides some insight into the differences in magnetic properties that are expected to exist in thin films and surfaces. The Stoner parameter and the DOS at the Fermi level depend on the chemical elements and the system s dimensionality and can thus be modified. The DOS at the Fermi level depends on the width of the d-band, which can be roughly described as... 

XPS has been used in almost every area in which the properties of surfaces are important. The most prominent areas can be deduced from conferences on surface analysis, especially from ECASIA, which is held every two years. These areas are adhesion, biomaterials, catalysis, ceramics and glasses, corrosion, environmental problems, magnetic materials, metals, micro- and optoelectronics, nanomaterials, polymers and composite materials, superconductors, thin films and coatings, and tribology and wear. The contributions to these conferences are also representative of actual surface-analytical problems and studies [2.33 a,b]. A few examples from the areas mentioned above are given below more comprehensive discussions of the applications of XPS are given elsewhere [1.1,1.3-1.9, 2.34—2.39]. 

Chapter 10 presents theoretical work on the origin of magnetism in Mn- and Cr-doped porous GaN with promise towards a room temperature dilute magnetic semiconductor, an essential component for spin-tronic applications. The large surface areas of porous material allow very high concentration of surface-specific atomic arrangements to be formed. Extensive computations have been performed on (Ga,Mn)N and (Ga,Cr)N systems from zero-dimensional clusters to one-dimensional nanowires, nanotubes, and nanoholes, two-dimensional surfaces and thin films, and three-dimensional crystals. 

In the first part of this chapter it will be reported on spin dependent transport and surface magnetic properties of itinerant magnetic substrates, thin Fe(l 10) and Co(OOOl) films evaporated on W(110), which were investigated by these electron emission techniques. Subsequently, the behavior of adsorbates will be discussed from the point of view whether they change the properties of the surface and whether they feel the magnetism of the underlying substrate. This discussion will be carried out for the example of oxygen which adsorbs dissociatively on the above mentioned surfaces. 

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