Crystal growth by Bridgman and Czochralski method of the ferromagnetic quantum critical material YbNi₄P₂

The tetragonal YbNi$_4$P$_2$ is one of the rare examples of compounds that allow the investigation of a ferromagnetic quantum critical point. We report in detail on two different methods which have been used to grow YbNi$_4$P$_2$ single crystals from a self-flux. The first, a modified Bridgman method, using a closed crucible system yields needle-shaped single crystals oriented along the $[001]$-direction. The second method, the Czochralski growth from a levitating melt, yields large single crystals which can be cut in any desired orientation. With this crucible-free method, samples without flux inclusions and a resistivity ratio at 1.8 K of RR$_{1.8\rm K}= 17$ have been grown.