Crystal growth of off-stoichiometric Co2Cr1-xAl1+x Heusler compounds: Avoiding the solid state miscibility gap

Co2CrAl is predicted as a promising candidate for half-metallic ferromagnetism. Unfortunately, synthesis of the stoichiometric composition is a challenge as the samples prepared so far using various techniques suffer from formation of secondary phases and consequently anomalous physical properties. Off-stoichiometric compounds have been explored as a possible approach to avoid the secondary phase precipitation. The Co2Cr0.8Al1.2, Co2Cr0.6Al1.4 and Co2Cr0.4Al1.6 compositions were synthesized using Floating Zone (FZ) technique as they melt incongruently. The secondary phase fraction was reduced as Cr was partially substituted by Al. FZ-grown Co2Cr0.4Al1.6 was obtained as a single phase, signifying that the composition is out of the two-phase region. Furthermore, combining the data with an earlier work on annealing of spinodally decomposed samples, valuable insight into the extent of immiscibility was obtained.