Question
is there any particular compost/soil, used to grow the mimosa from seed ?

Answer
Hi Chris,
Thanx for your question.  I apologize for the dealy in responding.  We are digging out from underneath nearly 10 inches /25cm of snow.  The biggest snow we've had in many years.  Anyway, I always use regular store-bought potting soil.  You can soak the seed overnight or nick them slightly on the end to speed up germination.  I find they germinate rather quickly (10 days or less) if you keep them warm 75癋/24癈 or above and moist but not soggy.  I hope this helps.
Tom