At low temperatures, strongly correlated materials, which typically contain partially filled d- or f-electron shells, often exhibit phases with interesting properties,which may be of both research value and technological significance. The mechanisms of phase formation in them if could be clarified, are believed to be ableto provide important insights not only into physics but also into the design ofnew materials. In this thesis, the experimental study of two strongly correlatedmaterials, Sr₂RuO₄ and CeAuSb₂ is presented.Sr₂RuO₄ is an unconventional superconductor, and a strong candidate for spin-triplet superconductivity. Its potential significance in relation to quantum computing also makes it of great scientific interest. In order to clarify the role of theVan Hove singularity (VHS) in its superconductivity, experimental study has beenperformed with the recently developed uniaxial strain methods. The experimentalresults suggest that as the sample is compressed towards the VHS, the transitiontemperature can be enhanced by a factor of =2.3 whilst the upper critical fieldcan be enhanced by a factor of more than ten. The experimental findings areintriguing and new possibilities are open for future study.CeAuSb₂ is a Kondo lattice system which has been speculated to be close toa quantum critical point. The similarity between some of its low temperatureproperties and those of a well-known quantum critical system Sr₃Ru₂O₇ makesit especially interesting. In this thesis, new magnetoresistivity and torque magnetometry measurements are used to clarify its low temperature phase diagram, andreveal the strength of its magnetic anisotropy.
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Uniaxial strain and high magnetic field investigation on materials with novel order parameters
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