Travelling solvent floating zone technique
During this project, high quality and large single crystals will be grown. The method of choice for the preparation of Heusler single crystals is the Travelling solvent floating zone technique (TSFZ). The preference for the TSFZ arises from the advantage also to grow crystals from materials which undergo an incongruent melting. Thus, only the growth by the TSFZ technique enables the control of the correct stoichiometry in Heusler crystals. Moreover, no crucibles are required and contamination and reaction with crucible materials are avoided.
Using the TSFZ, two rods of the material (seed and feed) are melted via an optical setup of mirrors (see figure below). In order to ensure homogeneity of the melt, both rods are rotated against each other. Via a vertical movement of the rods, the melting zone travels through the rod. This leads to a directional solidification and crystallisation. Impurities usually stay within the melt or stay at the surface of the crystal and can therefore easily be removed. Control and optimization of the crystal growth is done by supervising and adapting the growth parameters such as type gas and pressure of the gas, speed of rotation, speed of pulling, composition of the rods and temperature of the melt. Temperature control using a pyrometer and stroboscopic based methods are unique capabilities of the facilities at IFW Dresden.