critical_temperature_nbti Function

  function critical_temperature_nbti(c_pt,B,St) result(critical_temperature) bind(C)
      type(c_ptr), value :: c_pt
      real(dp), value :: B,St
      real(dp) :: critical_temperature
      real(dp) :: Blim,bb0,tt,Tc,Blow

      type(nbti_cfg_t), pointer :: nbti_ptr
      call c_f_pointer(c_pt,nbti_ptr)

      ! M.S.Lubell, Scaling formulas for critical current and critical field
      ! for commercial NbTi, IEEE Trans. Mag. ,19, (1983).      

      Blow=1.0e-3_dp
      Blim=max(abs(B),Blow)
      bb0 = Blim/nbti_ptr%Bc20

      if(bb0>0.0_dp .and. bb0<1.0_dp) then
         tt = (1.0_dp-bb0)**(1.0_dp/nbti_ptr%nu)
      else if(abs(bb0)<=1.0e-12_dp) then
         tt = 1.0_dp
      else if(bb0>1.0_dp) then
         tt = 0.0_dp
      endif
      Tc = nbti_ptr%Tc0_p * tt
      critical_temperature = Tc
  end function critical_temperature_nbti