Variation in energy stored and dissipated in type-II superconductor in   applied ac magnetic field with relative phase of two sinusoidal components of   the field
  We show that both the energy stored and dissipated by a system with hysteretic nonlinearity in an applied field varies with the relative phase of the sinusoidal components of the field, even if the magnitude of these components, and thus an effective value of the field, are kept constant. The explored system is a type-II superconductor in the critical state subjected to a time varying applied magnetic field. Complete analytical expressions for hysteresis loops, determined from basic physical phenomena, are known for this system. A theoretically predicted variation in the energy is in good agreement with our experimental measurements. 
Zdenek Janu and Tymofiy Chagovets
cond-mat.supr-con