PHYS07200604007 Manas Kumar Dala - Homi Bhabha National ...

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spectroscopy and O K edge x-ray absorption spectroscopy we have studied the temperature dependence of the near Fermi level electronic structure in the electron doped CMR, Ca 0.86 Pr 0.14 MnO 3 . We found that the temperature dependent changes in the electronic structure is consistent with the conductivity behavior of the electron doped systems in general. As the temperature is lowered from 293 K a feature due to the e g states starts appearing near the E F . This increase in the DOS is a signature of the semi-metallic behavior of the sample in the range 110 - 300 K. Surprisingly, though the resistivity measurement on this sample showed an insulating behavior below its transition temperature T c (110 K), the intensity of this feature further increases below the T c . Further, we have found an increase in the e g band width (W) also at low temperatures. It was also interesting to note that the increase in the near E F DOS in this compound is apparently different in nature from that associated with the pseudogap formation in the other systems like Pr 1−x Sr x MnO 3 . We have discussed our results from the point of view of phase sepation models considering the temperature dependent structural changes and consequent localization of the electrons in a narrow e g band. xii
Bibliography [1] R. von Helmolt, J. Wecker, B. Holzapfel, L. Schultz, and K. Samwer; Phys. Rev. Lett. 71, 2331 (1993). [2] Y. Tokura, A. Urushibara, Y. Moritomo, T. Arima, A. Asamitsu, G. Kido and N. Furukawa; J. Phys. Soc. Jpn. 63, 3931 (1994). [3] A. Urushibara, Y. Moritomo, T. Arima, A. Asamitsu, G. Kido, and Y. Tokura; Phys. Rev.B 51, 14103 (1995). [4] Y. Tomioka, A. Asamitsu, Y. Moritomo, and Y. Tokura, J. Phys. Soc. Jpn 64, 3626 (1995). [5] G. H. Jonker and J. H. Van Santen Physica 16, 337 (1950). [6] C. Zener, Phys. Rev. 81, 440 (1951). [7] C. Zener, Phys. Rev. 82, 403 (1951). [8] P. W. Anderson and H. Hasegawa, Phys. Rev. 100, 675 (1955). [9] P. G. de Gennes, Phys. Rev. 118, 141 (1960). [10] A. J. Millis, B. I. Shraiman, and P. B. Lttlewood, Phys. Rev. Lett. 74, 5144 (1995). [11] A. J. Millis, Nature 392, 147 (1998). [12] A. Moreo, S. Yunoki, and E. Dagatto, Science 283 2034 (1999). [13] A. Moreo, M. Mayr, A. Feiguin, S. Yunoki, and E. Dagotto, Phys. Rev. Lett. 84 5568 (2000). xiii
Page 1 and 2: SPECTROSCOPIC INVESTIGATIONS OF THE
Page 3 and 4: iii To My Parents
Page 5 and 6: Maharana, P. Khare, D. K. Basa, K.
Page 7 and 8: List of Publications/Preprints [1]
Page 9 and 10: Synopsis The perovskite type mangan
Page 11: to the t 2g and e g spin-up states
Page 15 and 16: Contents CERTIFICATE Acknowledgemen
Page 17 and 18: List of Figures 1.1 Temperature dep
Page 19 and 20: 2.2 Schematic view of the energetic
Page 21 and 22: 3.4 O K edge x-ray absorption spect
Page 23 and 24: Chapter 1 Introduction 1
Page 25 and 26: Introduction 3 The temperature and
Page 27 and 28: Introduction 5 Figure 1.2: Schemati
Page 29 and 30: Introduction 7 Figure 1.4: A schema
Page 31 and 32: Introduction 9 Figure 1.6: Schemati
Page 33 and 34: 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
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Page 57 and 58: Experimental Techniques 35 negative
Page 59 and 60: Experimental Techniques 37 ∆E = E
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Experimental Techniques 41 ( ) dσ
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Experimental Techniques 43 The expe
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Experimental Techniques 45 are weld
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Experimental Techniques 47 Figure 2
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Bibliography [1] H. Hertz, Ann. Phy
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Experimental Techniques 57 [35] K.
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Chapter 3 Electronic Structure of P
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Electronic Structure of Pr 0.67 Ca
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Bibliography [1] I. G. Deac, J. F.
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Chapter 4 Electronic Structure of P
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Electronic Structure of Pr 1−x Ca
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Electronic Structure of Ca 0.86 Pr
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Bibliography [1] C. Zener, Phys. Re
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Summary and Conclusions 109 In this
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