The thermal‐imaging floating zone technique can be used to grow crystals of yttrium iron garnet (Y3Fe5O12), aluminum‐doped yttrium orthoferrite (YFe0.88Al0.12O12), and magnetite (Fe3O4), which represent peritectic compounds, solid‐solution crystals, and atmosphere‐sensitive materials, respectively. The reactions involved in floating zone crystal growth are explained on the basis of phase diagrams. A review of crystal growth reports, including unpublished findings by the present authors, demonstrates how the crystallization processes, the reaction with the ambient atmosphere, and the composition variation in the obtained crystals can be explained or controlled on the basis of phase equilibrium. The floating zone technique is applicable to a variety of materials and remains a handy tool for materials research; however, its industrial application may be