ISBN 9783843909785

978-3-8439-0978-5, Reihe Physik

Gerd Neuber
Optical Spectroscopy on NiMnIn, Ni₂MnIn Heusler Alloys, and ZnyLa_2-xSr_xCu_1-yO₄

227 Seiten, Dissertation Universität Hamburg (2012), Softcover, B5

Zusammenfassung / Abstract

This thesis presents the results of the measurements of the optical properties of Ni2MnIn Heusler alloy thin film samples, and of untwined single crystal samples of the underdoped cuprate Zn0.05La1.95Sr0.05Cu0.95O4.

For the measurement of the magneto-optical properties of the Heusler alloys a magneto-optical extension of a commercial SE-850 spectral ellipsometer has been developed as a part of this thesis.

As another part of the thesis, an extension for the beamline I measuring station at the DORIS III storage ring has been developed, allowing for vacuum ultraviolet (VUV) reflectance spectroscopy.

Chapter 2 of the thesis treats the classical interaction of light with matter by means of the Drude-Lorentz model, yielding a general formula for the complex dielectric function of solids. Linear response functions like the dielectric function, the complex refractive index, and the optical conductivity as well as relations between them are discussed also. The quantum mechanical treatment with first-order time-dependent perturbation theory again yields the Drude-Lorentz model but with a new interpretation of the parameters in the model. Fitting the model to the measured optical response of materials aids the understanding of their band structure. The basic ellipsometry principles are evolved, followed by the generalization to optical anisotropic solids, introducing tensors for the response functions. The Kramers-Kronig transformations are applied for the computation of the dielectric functions from reflectance spectra. Subsequently, the classical and quantum mechanical theory of the magneto-optical Kerr-effect is discussed. Chapter 2 ends with a survey of the characteristic properties of Heusler alloys and cuprates.

Chapter 3 deals with the details of the experimental setups of the SE-850 spectral ellipsometer, the SGME extension, the beamline I, and the gold mesh extension.

In chapters 4 and 5 the measurements of the optical and magneto-optical response of several Ni2MnIn Heusler alloys and of Zn0.05La1.95Sr0.05Cu0.95O4 are presented and interpreted with the help of the findings in chapter 2.

In chapter 6 the results are summed up and an outlook on the further development of the introduced setups is given.