Diploma - Max Planck Institute for Solid State Research

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Figure 3.3: (a) general setup of a photoemission endstation at synchrotron facilities, (b) on the left-hand side: the 1 3 ARPES, (c) on the right-hand side: the SIS ARPES endstation 22 3 Experimental foundations
23 4 EuRh 2 Si 2 – semi-localized electrons 4.1 Overview – properties and classification The ternary compound EuRh 2 Si 2 crystallizes in the tretragonal body-centered ThCr 2 Si 2 structure. The respective lattice parameters and Wyckoff positions are given in tab. 4.1 (experimental and calculated relaxed 1 parameters). Surprisingly, the differences between the computionally relaxed parameters and the experimental ones are rather small (an indication of the well-chosen basis set in FPLO and keeping the 4f occupation fixed a suitable approximation – at least for total energy). The crystal structure is depicted in fig. 4.5a, whereas the tretagonal unit cell is bordered by dotted lines. It is evident, that this is a layered structure with respect to the [001] direction. The main transport properties and the phase diagram of EuRh 2 Si 2 have already been explored [3], hence only a short review is given here. Since similar ternary compounds show for example Heavy-Fermion behaviour (YbRh 2 Si 2 in [5]), superconductivity (CeRh 2 Si 2 in [6]), mixed-valent (EuPd 2 Si 2 in [37, 38]) or spin-density wave behaviour (EuFe 2 As 2 in [4]) one expects also interesting electronic properties and magnetic behaviour in EuRh 2 Si 2 . Belonging to the stable divalent europium materials it reveals an antiferromagnetic (AF) ordered phase of the localized 4f 7 moments below 25 K, the exact configuration of which is unknown. It is supposed to be a ferromagnetic coupling in the Eu plane and an AF order between the respective layers [3]. The energy gain of magnetic order is small and thus yet a small pertubation induces a different magnetic order or partially non-magnetic contribution to the ground state. Therefore 1 In the case of the lattice constants the computational relaxation has been performed by a self-written implementation of the gradient method minimizing the total energy. Plotting the energy functional for a deviation of 15% from the experimental lattice parameters shows a smooth energy surface. The Wyckoff positions were force-minimized afterwards by the implemented procedure in FPLO. In both cases, the total error of the computation has been smaller than the experimental one and the former has been rounded to the accuracy of the latter. Table 4.1: (a) lattice constants and (b) Wyckoff positions: experimental [36] and calculated relaxed parameters (fplo 9.07.41, LDA, 4f 7 unpolarized open core) (a) lattice constants exp. [Å] relaxed [Å] a x 4.107 4.089 a y 4.107 4.089 a z 10.25 10.244 (b) Wyckoff positions exp. relaxed x y z x y z Eu 0 0 0 0 0 0 Rh 0 0.5 0.25 0 0.5 0.25 Si 0 0 0.375 0 0 0.375
Page 1 and 2: - Photoemission on EuRh 2 Si 2 - di
Page 3: Abstract A thorough knowledge of co
Page 7: vii Nomenclature AF APW ARPES BO BZ
Page 10 and 11: 2 1 Introduction conflicting limits
Page 12 and 13: 4 2 Theoretical foundation fore the
Page 14 and 15: 6 2 Theoretical foundation system a
Page 16 and 17: 8 2 Theoretical foundation such a s
Page 18 and 19: 10 2 Theoretical foundation Figure
Page 20 and 21: 12 2 Theoretical foundation Figure
Page 22 and 23: 14 2 Theoretical foundation Fi
Page 25 and 26: 17 3 Experimental foundations 3.1 P
Page 27 and 28: 3.2 General setup 19 Figure 3.2: ch
Page 29: 3.4 SLS: SIS-HRPES 21 1 3 ARPES the
Page 33 and 34: 4.1 Overview - properties and class
Page 49 and 50: 4.2 Hybridization: localized versus
Page 61 and 62: 4.3 Perspective: quasi-linear dispe
Page 63: 4.3 Perspective: quasi-linear dispe
Page 66 and 67: 58 5 Summary to the f-d interaction
Page 68 and 69: 60 Bibliography [13] B. Kramer. A P
Page 70 and 71: 62 Bibliography [44] T. M. Rice and
Page 72 and 73: 64 Bibliography [75] Hari C. Manoha
Page 75: List of Tables 67 List of Tables 2.
Page 79: Erklärung Hiermit versichere ich,

Diploma - Max Planck Institute for Solid State Research

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