High Tc Superconductors and Related Transition Metal Oxides
When initiating this book and inviting friends of K. Alex Müller to send c- tributions to it in order to honor his 80’th birthday, we frequently were told that it would be dif?cult to write anything related to high temperature - perconductivity. It seemed that most of his friends and colleagues associate almost exclusively high temperature superconductivity with his name and have forgotten that K. Alex Müller’s scienti?c career is more tightly bound to phase transitions, critical phenomena, electron paramagnetic resonance (EPR), and ferroelectricity than to superconductivity, even though he caused – together with Georg Bednorz – a revolution in this ?eld. More than half of his research life concentrates on the above mentioned phenomena and - jor breakthroughs have been achieved by him in this area. Starting point was IV the investigation of the electron paramagnetic resonance of Mn in SrTiO 3 whereheobservedthatdistortedregimesappearinthenominallycubicphase. A homogeneous state is only realized when the crystal is in the tetragonal phase. Even though SrTiO remained in the center of his research interests 3 early on,the Jahn–Teller effect was fascinating him. Experimentally and th- reticallyhestartedvariousprojectsinthis?eldwhichhastheuniqueproperty thatavibronicstatedominatesthephysics,whereelectronicandionicdegrees offreedomareundistinguishable. Thisstateisaconsequence ofacompetition between enhancing the entropy and lowering the energy of the system and intimately related to ferrodistortive transitions. These have been investigated in detail by him concentrating on the rotational instability of the oxygen - tahedral in perovskites where he showed that the rotationangle plays the role of an order parameter.
The invited contributing authors of the book are representatives of novel approaches to enlarge the understanding of the complexity of transition metal oxidesEspecially lattice effects which have been ignored for a long time are addressed in detail