Kinetic arrest of direct and reverse martensitic transformation and exchange bias effect in [formula omitted] melt spun ribbons

Phase coexistence phenomena related to direct and reverse martensitic transformation have been studied in melt spun ribbons of the magnetic shape memory alloy [formula omitted]. For magnetic fields above 10 kOe martensitic transformation undergoes a progressive kinetic arrest. The metastable character of the field-cooled frozen fraction of austenite into martensite was verified. An atypical incomplete reverse martensitic transformation of thermal origin was also observed. The zero-field cooled thermomagnetization curve measured at 50 kOe shows a decrease below 30 K that was accompanied by the occurrence of exchange bias effect suggesting the strengthening of antiferromagnetic interactions in martensite in such temperature range.