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Mirror furnace (jpeg, 37k)General

The crystal laboratory at the Walther-Meißner-Institute has been set up starting in April 2000. Until today it has developed a high degree of specialization in the growth and characterization of single crystals of various transition metal oxides. The WMI research activities in the field of crystal growth are mainly focused on high-temperature superconductors, where the preparation of high quality single crystal is a central projects within the Research Unit FOR 538 of the German Science Foundation (DFG) entitled "Doping dependence of phase transitions and ordering phenomena in cuprate superconductors".

Within a more recent research activity the WMI crystal laboratory contributes to the research program of the Cluster of Excellence "Origin of the Universe" at the Technical University of Munich by the growth of large detector crystals of CaWO4.

Right: Pr1.85Ce0.15CuO4 single crystal growth in the four-mirror furnace at WMI

High Temperature Superconductors

phase diagram (jpeg 20k) To be able to probe the whole phase diagram both on the hole- and electron-doped side of the phase diagram of the cuprate superconductors, a variety of compounds are grown as single crystals:
On the hole doped side we grow single crystals of the 123 system with various doping level. High purity REBa2Cu3O7-δ (RE = rare earths) crystals are grown in specially developed inert BaZrO3 crucibles. The other compounds of the high temperature superconductors are grown by a traveling solvent floating zone technique in an optical mirror furnace.  On the hole doped side these systems are La2-xSrxCuO4, Bi-2223, Bi-2212, and Bi-2201.
For probing the electron doped side of the phase diagram, single crystals of the 214–systems Pr2-xCexCuO4 and Nd2-xCexCuO4 are prepared.

Left : Generic phase diagram of the cuprate superconductors
Y-123 (jpeg, 5k)
Nd-123 (jpeg, 3k)
La-214 (jpeg, 9k)
YBa2Cu3O7-δ crystals in a BaZrO3 crucible
NdBa2Cu3O7-δ crystal
La2-xSrxCuO4 single crystal grown in a mirror furnace

CaWO4 (jpeg, 8k)Detector Crystals

The WMI crystal laboratory contributes to the Cluster of Excellence "Origin of the Universe" at the Technical University of Munich by the growth of large detector crystals of CaWO4. These crystals with diameters of several centimeters are grown in pure rhodium crucibles by the Czochralski method.

Bulk Materials

We also prepare high purity targets for the deposition of thin films and heterostructures of various transition metal oxides by the PLD process. Examples are the ferromagnetic double perovskites, magnetite (Fe3O4), the ferromagnetic semiconductor (Zn,Co)O, or multiferroic materials such as BiFeO3 or BiCrO3.

Right: CaWO4 single crystal above the melt, Tm = 1600°C