The spin-wave stiffness constant D and the Curie temperature TC for series of L21 phase in Co2CrGa, Co2MnGa, Co2Mn(Al1-xSix) , Co2Fe(Al 1-xSix), and Co2Fe(Ga1-xSi x) Heusler alloys were evaluated from the thermomagnetization measurements. For the Co2CrGa, Co2MnGa, and Co 2Mn(Al1-xSix) alloys, there was a linear relation between D and TC. The tendency between D and TC was different from that for Co2Fe(Al1-xSix) and Co2Fe(Ga1-xSix) alloys, that is, TC was in the temperature region from 1040 to 1100 K indicating weak concentration dependence, whereas D was sensitive to the composition. For example, D changed from 2.28 meV · nm2 for x=1 (Co2FeSi) to 5.24 meV · nm2 for x=0 (Co2FeGa) in the case of Co 2Fe(Ga1-xSix) alloys. It was suggested that magnetic stability against the temperature of the Co-based Heusler alloys containing Fe element was governed not only by the spin-wave excitation but also by the other kinds of excitation.
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