Intermediate valent systems
EuPd2Si2, EuT2P2 (T=Ru,Fe,Co), YbInCu4 contain rare elements with a nearly filled or half-filled 4f shell. The lanthanide shows a strong change of its valence state upon changing temperature or pressure.
Strongly correlated electron systems, Quantum criticality
In YbNi4P2, YbNi4(P1-xAsx)2, YbRh2Si2, CeTPO (T=Ru,Fe) the conduction electrons interact strongly with each other and with the local magnetic moments of the rare-earth ions. The systems allow for studying quantum critical points.
Materials showing 4f local moment magnetism
The compounds LnT2Si2 (Ln= lanthanide, T=Rh,Ir) are of particular interest. Besides a large variety of different arrangements of their magnetic moments in the antiferromagnetic bulk or the occurrence of the Kondo effect, many of these materials host surface states which are tunable with temperature and make them interesting model systems for spintronic applications.
Materials showing 3d itinerant (+ 4f local moment) magnetism
Systems like LnCo2P2, GdCo2Si2, LnMn2X2 (Ln=lanthanide, X=Si,Ge) are characterized by high magnetic ordering temperatures occurring due to the ordering of the transition metals itinerant electrons. Some show additional local moment magnetism of the 4f local moments.
Topological materials and skyrmion materials
Oxides and semimetals
EuO, EuS serve as Heisenberg model systems and can be grown at temperatures higher than 2300°C.
For instance F-doped LaOFeAs shows unconventional superconductivity with Tc above 50K.
Heavy fermion superconductors
The compounds YbRh2Si2, CeIrIn5 show unconventional superconductivity at very low temperatures.
Crystal growth methods
- Czochralski technique under enhanced Ar pressure
- Bridgman method
- High-temperature solution growth (self-flux, external flux)
- Vapour transport