  A novel vertical hysteresis loop shift is observed for a bilayer thin film of
Ni80Fe20/SrRuO3 (1:2 thickness ratio) on SrTiO3 substrate, after field cooled
through the Curie temperature ~125 K of SrRuO3, whereas no shift is found for
zero field cooled measurement. The vertical shift is noticed below ~125 K which
increases with decreasing temperature and reaches a maximum of 33% at 2 K. The
vertical shift is modelled closely using micromagnetic simulations. It is shown
that the amount of vertical shift depends on the competition between the
relative thicknesses and the anisotropies of the two films governed by Spring
Thickness law and Imperial Law, respectively. We propose a generalized model of
vertical shift which is applicable for other material systems, and hence could
be informative for use of vertical shift in future spintronic devices.
