Method to calculate performance of a magnetic element comprising a reference bilayer including a ferromagnetic reference layer having a reference magnetization and an antiferromagnetic layer pining the reference magnetization by exchange-bias, the antiferromagnetic layer comprising a metallic polycrystalline material having a grain volume distribution; the method comprising: measuring an exchange-bias field (H ex) of the.antiferromagnetic layer at selected exposure temperatures (Ts), under selected in-plane exposure magnetic fields applied to the reference bilayer, during an exposure time (τ S); characterised in that the method is further comprising: fitting a grain volume distribution function to the measured exchange-bias fields (H ex) to determine at least one distribution parameter characterizing the volume distribution of the grains and at least one magnetic parameter characterizing the magnetic properties of the antiferromagnetic layer; calculating a reference angle (θ FM) corresponding to an in-plane variation in the direction of the reference magnetization, as a function of a direction of the exposure magnetic field; calculating the exchange bias field (H ex) for any value of the in-plane exposure magnetic field, exposure temperature (T S) and exposure time (τ S), using the calculated reference angle (θ FM) and determined said at least one distribution and magnetic parameters in the grain volume distribution function. measuring an exchange-bias field (H ex) of the.antiferromagnetic layer at selected exposure temperatures (Ts), under selected in-plane exposure magnetic fields applied to the reference bilayer, during an exposure time (τ S); characterised in that the method is further comprising: fitting a grain volume distribution function to the measured exchange-bias fields (H ex) to determine at least one distribution parameter characterizing the volume distribution of the grains and at least one magnetic parameter characterizing the magnetic properties of the antiferromagnetic layer; calculating a reference angle (θ FM) corresponding to an in-plane variation in the direction of the reference magnetization, as a function of a direction of the exposure magnetic field; calculating the exchange bias field (H ex) for any value of the in-plane exposure magnetic field, exposure temperature (T S) and exposure time (τ S), using the calculated reference angle (θ FM) and determined said at least one distribution and magnetic parameters in the grain volume distribution function. fitting a grain volume distribution function to the measured exchange-bias fields (H ex) to determine at least one distribution parameter characterizing the volume distribution of the grains and at least one magnetic parameter characterizing the magnetic properties of the antiferromagnetic layer; calculating a reference angle (θ FM) corresponding to an in-plane variation in the direction of the reference magnetization, as a function of a direction of the exposure magnetic field; calculating the exchange bias field (H ex) for any value of the in-plane exposure magnetic field, exposure temperature (T S) and exposure time (τ S), using the calculated reference angle (θ FM) and determined said at least one distribution and magnetic parameters in the grain volume distribution function.