Structural and magnetization changes at high temperature in Co50Mn30In20 alloy.

In this work we report on microstructural and magnetic characterization of Co50Mn30In20 alloy melt-spun ribbons in its as-cast state and after being annealed at 923 K during 5 h. Microstructure was analysed by means of differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques, while magnetic measurements (hysteresis loop and magnetization) were performed in the temperature range 1.8-1000 K. XRD measurements confirm the presence of Heusler phase Co2MnIn in the annealed material with crystallites sizing around 35 nm. Ferromagnetic ordering temperatures in Co-based Heusler systems (Co2MnIn) are considerably higher than in the corresponding Ni2MnIn ones. In this case, T(c) = 520 K for the annealed sample is lower than the corresponding one (T(c) = 550 K) for the as-cast ribbon. At around 840 K, the very abrupt magnetization change for the annealed sample is higher than the one obtained for the as-cast ribbon. This temperature value is the same than the recrystallization phase transition temperature detected in the DSC measurement.