PHYS07200604007 Manas Kumar Dala - Homi Bhabha National ...

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Electronic Structure of Pr 1−x Ca x MnO 3 90 Pr 4d Temp = 300 K Intensity (arb. unis) 0.4 0.3 0.2 130 120 110 Binding Energy (eV) (a) 100 Pr 4d Temp = 77 K Intensity (arb. units) 0.4 0.33 0.2 130 120 110 Binding Energy (eV) (b) 100 Figure 4.8: The Pr 4d core-level XPS (Mg Kα) spectra of Pr 1−x Ca x MnO 3 taken at room temperature (a) and 77 K (b).
Electronic Structure of Pr 1−x Ca x MnO 3 91 2p could be due to the increase in the effective Mn valence state from Mn 3+ towards Mn 4+ . The binding energy shift incase of Ca 2p and Pr 4d core levels could possibly due to the shift in the chemical potential [33, 40]. The low temperature data shows a smaller value for this chemical potential shift. Such a suppression of the chemical potential shift have been observed earlier in other transition metal oxides [41, 42] is mostly due to the formation of stripes. According to the phase separation model, a pinning of the chemical potential is consequence of the mixed phase nature of these materials. The numerical studies [1, 3] have indeed shown the pinning of chemical potential in the composition range, where the phase separation is realized. These results also support the model of phase separation in the Pr 1−x Ca x MnO 3 system. 4.4 Conclusions Using UV photoelectron spectroscopy and inverse photoelectron spectroscopy we have deduced some of the important energy scales in the Pr 1−x Ca x MnO 3 system. Our photoemission studies across the FM-AFM phase boundary show that the pseudogap formation in these compounds occur over an energy scale of 0.47±0.01 eV. From a combined analysis of the photoemission and inverse photoemission spectra we also have found the energy required for the transfer of Mn 3d e g electrons between the adjacent Mn sites to be of the order of ∼ 2.8±0.2 eV. Though an accurate measurement of these energies are not possible due to the inherent limitations of the compounds and the technique, our results give an upper bound of them. Further, we have discussed our results from a possible phase separation scenario. From the core level study of Pr 1−x Ca x MnO 3 , we observed a suppression of chemical potential shift for 77 K spectra compared to that of room temperature. These results support the model of phase separation in Pr 1−x Ca x MnO 3 system.
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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
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Introduction 13 Figure 1.10: A sche
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Introduction 15 Figure 1.12: Schema
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Introduction 17 Figure 1.13: Phase
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Bibliography [1] R. von Helmolt, J.
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Introduction 21 [31] Damien Saurel,
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Chapter 2 Experimental Techniques 2
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Experimental Techniques 25 Figure 2
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Experimental Techniques 27 Let us n
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Experimental Techniques 29 and G(k,
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Experimental Techniques 31 Figure 2
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Experimental Techniques 33 point wi
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Experimental Techniques 35 negative
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Experimental Techniques 37 ∆E = E
Page 61 and 62: Experimental Techniques 39 Figure 2
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 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 111: 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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