High-pressure optical floating-zone growth of Li(Mn,Fe)PO4 single crystals

Publication date: 15 March 2017
Source:Journal of Crystal Growth, Volume 462
Author(s): Christoph Neef, Hubert Wadepohl, Hans-Peter Meyer, Rüdiger Klingeler
Mm-sized LiMn1−x Fe x PO4 single crystals with $0⩽x⩽1$ were grown by means of the traveling floating-zone technique at elevated Argon pressure of 30bar. For the various doping levels, the growth process was optimized with respect to the composition-dependant effective light absorption and transparency of the materials. A convex crystal/melt interface, determined by the angle of incident light, was identified to be particularly crucial for a successful growth. The resulting large single crystalline grains are stoichiometric. Structure refinement shows that lattice parameters as well as the atomic positions and bond lengths linearly depend on the Mn:Fe-ratio. Oriented cuboidal samples with several mm³ of volume were used for magnetic studies which imply an antiferromagnetic ground state for all compositions. The Néel-temperature changes from $T_{\mathrm{N}}$ =32.5(5)K in LiMnPO4 to 49.5(5)K in LiFePO4 while the easy magnetic axis in the ordered phase flips from the crystallographic a- to the b-axis upon Fe-doping of $x\<0.2$.