Use of superparamagnetic temperature transition measurement in nanocrystalline alloys to determine low crystalline fractions by modeling of the weak-coupling behavior

•A method to measure nanocrystalline samples crystalline fraction fc is presented.•Superparamagnetic transition temperature Ttr is used to determine fc.•The Ttr crystalline fraction dependency is modelled.•The intergrain dipolar coupling an interphase exchange coupling are considered.•Experimental measurement have beeb carried out and are presented.