code: def G_mag(self, T):
          
  
          tau = T / self.Tc_mag
  
          if tau <= 1.0:
              g = 1 - (self._A_mag/tau +
                       self._B_mag*(tau**3/6 + tau**9/135 + tau**15/600)) /\
                      self._D_mag
          else:
              g = -(tau**-5/10 + tau**-15/315 + tau**-25/1500)/self._D_mag
  
          return R*T*math.log(self.beta0_mag + 1)*g
docs: Calculate the phase's magnetic contribution to Gibbs energy at the
          specified temperature.
  
          :param T: [K] temperature
  
          :returns: [J/mol] The magnetic Gibbs energy of the compound phase.
  
          Dinsdale, A. T. (1991). SGTE data for pure elements. Calphad, 15(4),
          317–425. http://doi.org/10.1016/0364-5916(91)90030-N