PHYS07200604007 Manas Kumar Dala - Homi Bhabha National ...

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Electronic Structure of Pr 0.67 Ca 0.33 MnO 3 64 300 K 77 K 5 X Difference (a) 300 K 110 K 5 X Difference (b) Intensity (arb. units) -1 -0.5 0 0.5 1 1.5 300 K 220 K 5 X Difference (d) -1 -0.5 0 0.5 1 1.5 300 K 150 K 5 X Difference (c) -1 -0.5 0 0.5 1 1.5 Binding Energy (eV) -1 -0.5 0 0.5 1 1.5 Figure 3.2: High-resolution photoemission spectra of the near-E F region of the valence band of Pr 0.67 Ca 0.33 MnO 3 . In (a) the spectrum taken below T c (red) is compared with the normal state (300 K) spectrum (blue). The difference spectrum (green) obtained by subtracting the spectra at 300 K from 77 K and multiplied by 5 is also shown in the panel. Similarly, in (b), (c), and (d) the near-E F spectra taken at 110, 150, and 220 K are compared with that taken at 300 K. The feature in the difference spectra corresponds to the tail feature A (e g↑ ) in Fig. 3.1. is quite small compared to B and C and is a signature of the insulating nature of this material. Earlier photoemission experiments on La 1−x Sr x MnO 3 also have shown that the intensity of this tail feature A is quite small [8, 20, 21, 22, 23]. The presence of the feature A is clear from Fig. 3.2, where we have shown the near-E F region of the valence band spectra taken with a higher resolution. Here, the spectra taken at different temperatures have been compared with those at room temperature. The figure also shows the difference spectra obtained by subtracting the room-temperature spectra from spectra taken at low temperatures. The feature in the difference spectra corresponds to A, which originates from the e g↑ states [22]. In order to estimate the relative changes in all the three features (A, B, and C) due to temperature, we have carefully fitted the whole valence band spectrum with
Electronic Structure of Pr 0.67 Ca 0.33 MnO 3 65 0.014 (a) 0.012 Normalized Intensity 0.01 0.6 0.55 0.5 0.45 (b) (c) 0.4 100 150 200 250 300 Temperature (K) Figure 3.3: Temperature dependence of the area of the three valence band features obtained from fitting the spectra with Lorentzian line shapes using a χ 2 iterative program. We have used an integral background, which was kept the same for all the spectra. The energy positions and FWHMs were determined by finding the best fit common to all the spectra by the iterative program. The final fit for all spectra at different temperatures were obtained with the same energy positions and FWHMs. (a), (b), and (c) correspond to the features A, B, and C positioned at -1.19, -3.49, and -5.63 eV with FWHMs 2.56, 1.93, and 1.37 eV respectively.
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SPECTROSCOPIC INVESTIGATIONS OF THE
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iii To My Parents
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Maharana, P. Khare, D. K. Basa, K.
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List of Publications/Preprints [1]
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Synopsis The perovskite type mangan
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to the t 2g and e g spin-up states
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Bibliography [1] R. von Helmolt, J.
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Contents CERTIFICATE Acknowledgemen
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List of Figures 1.1 Temperature dep
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2.2 Schematic view of the energetic
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3.4 O K edge x-ray absorption spect
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Chapter 1 Introduction 1
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Introduction 3 The temperature and
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Introduction 5 Figure 1.2: Schemati
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Introduction 7 Figure 1.4: A schema
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Introduction 9 Figure 1.6: Schemati
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Introduction 11 Figure 1.8: Differe
Page 35 and 36: Introduction 13 Figure 1.10: A sche
Page 37 and 38: Introduction 15 Figure 1.12: Schema
Page 39 and 40: Introduction 17 Figure 1.13: Phase
Page 41 and 42: Bibliography [1] R. von Helmolt, J.
Page 43 and 44: Introduction 21 [31] Damien Saurel,
Page 45 and 46: Chapter 2 Experimental Techniques 2
Page 47 and 48: Experimental Techniques 25 Figure 2
Page 49 and 50: Experimental Techniques 27 Let us n
Page 51 and 52: Experimental Techniques 29 and G(k,
Page 55 and 56: Experimental Techniques 33 point wi
Page 57 and 58: Experimental Techniques 35 negative
Page 59 and 60: Experimental Techniques 37 ∆E = E
Page 63 and 64: Experimental Techniques 41 ( ) dσ
Page 65 and 66: Experimental Techniques 43 The expe
Page 67 and 68: Experimental Techniques 45 are weld
Page 77 and 78: Bibliography [1] H. Hertz, Ann. Phy
Page 79 and 80: Experimental Techniques 57 [35] K.
Page 81 and 82: Chapter 3 Electronic Structure of P
Page 83 and 84: Electronic Structure of Pr 0.67 Ca
Page 85: Electronic Structure of Pr 0.67 Ca
Page 95 and 96: Bibliography [1] I. G. Deac, J. F.
Page 99 and 100: Chapter 4 Electronic Structure of P
Page 101 and 102: Electronic Structure of Pr 1−x Ca
Page 119 and 120: Electronic Structure of Ca 0.86 Pr
Page 127 and 128: Bibliography [1] C. Zener, Phys. Re
Page 131 and 132: Summary and Conclusions 109 In this
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PHYS07200604007 Manas Kumar Dala - Homi Bhabha National ...

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