Contents ........................................................ I
List of Figures ............................................... III
List of Symbols and Abbreviations ............................. VII
Introduction ................................................... IX
1 Theoretical concepts ......................................... 1
1.1 Heavy-fermion systems ................................... 1
1.1.1 Single-impurity Koiido effect .................... 1
1.1.2 Koiulo-lattice systems and RKKY interaction ...... 3
1.2 Landau Fermi-liquid behavior ............................ 6
1.3 Routes to non-Fermi-liquid behavior ..................... 7
1.3.1 Quantum critical phenomena ....................... 8
1.4 Pressure response of the Co and Yb-atoms ............... 14
2 Experimental methods ........................................ 17
2.1 High-pressure techniques ............................... 17
2.1.1 Pressure cells .................................. 18
2.1.2 Determination of pressure ....................... 20
2.1.3 Electrical-resistivity measurements ............. 23
2.1.4 A.c. magnetic-susceptibility measurements ....... 23
2.2 Measurement instruments ................................ 24
3 Transport studies of the HF metal YbIr2Si2 under high
pressure .................................................... 25
3.1 Crystal structure ...................................... 27
3.2 Short overview of the physical properties of the HF
metal YbRh2Si2 ......................................... 29
3.3 Yb(Rh0.94Ir0.06)2Si2: external pressure υs. chemical
substitution ........................................... 35
3.4 Effect of the magnetic field on Yb(Rh0.94Ir0.06)2Si2
under pressure1 ........................................ 40
3.5 Discussion: T - p phase diagram erf
Yb(Rh0.94Ir0.06)2Si2 ..................................... 46
3.6 Effect erf pressure on the heavy-fermion system
YbIr2Si2 ............................................... 48
3.6.1 Physical properties erf YbIr2Si2 at ambient
pressure ........................................ 49
3.6.2 Evolution erf the high-temperature physical
properties of YbIr2Si2 with pressure ............ 52
3.6.3 Effect of pressure on the crystal lattice in
YbIr2Si2 ........................................ 58
3.6.4 Pressure dependence of the physical properties
of YbIr2Si2 at low temperatures ................. 61
3.6.5 Effect of magnetic field on YbIr2Si2 under
pressure ........................................ 68
3.7 Discussion ............................................. 73
3.8 Summary ................................................ 85
4 Pressure studies on the FM Kondo-lattice system CeRuPO ...... 89
4.1 Sample preparation and crystal structure ............... 90
4.2 Overview of the ambient-pressure properties of the
CeTPO family ........................................... 92
4.2.1 Ferromagnetism in the Kondo-lattice system
CeRuPO .......................................... 93
4.3 Evolution of the ground-state properties of CeRuPO
under pressure ......................................... 99
4.4 Electrical-resistivity studies on CeRuPO at low
temperatures .......................................... 115
4.4.1 Electrical resistivity in the magnetically
ordered state .................................. 115
4.4.2 Study of the PM ground state of CeRuPO by
resistivity .................................... 120
4.5 Evolution of Kondo and CEF energy scales with
pressure .............................................. 122
4.6 Discussion and summary ................................ 129
5 Conclusion ................................................. 133
Bibliography .................................................. 137
Acknowledgements .............................................. 147
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