The magnetic properties and amorphous formation ability of Pr-based alloys have been reported and discussed. In this paper, Pr 90 Fe 10 alloys were studied to reveal the solidification behavior associated with undercooling, magnetic properties of the metastable phase, and relation between undercooling and metastable phase formation by using the gas flow levitation method. The samples were solidified at various cooling rates from approximately 50 K/s to approximately 270 K/s. Undercooling increased with the cooling rate. According to the results of the SEM-EDS analysis, the Pr 90 Fe 10 samples that solidified at high undercooling conditions in eutectic reactions consist of the primary -Pr, eutectic -Pr, and metastable phases whereas the samples that solidified at low undercooling conditions in eutectic reactions consist of the primary -Pr, eutectic -Pr, and Pr 2 Fe 17 phases. Additionally, the magnetic properties changed due to the undercooling.