  The vortex phases in type-II superconductors are very important since they
determine many magnetic and electric properties of the parent compound.
However, a universal tool to characterize the vortex phases is still lacking.
We demonstrate in a type-II superconductors YBa2Cu3O7-x polycrystal sample that
its vortex phases and phase boundaries can be comprehensively studied by a
magnetoelectric technique. In this method, a thin piezoelectric material
0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3(PMN-PT) is mechanically bonded with YBa2Cu3O7-x
to form a laminate structure and act as a strain gauge. The phase diagram of
the YBa2Cu3O7-x polycrystalline was explored by this method. Surprisingly, it
can accurately estimate the Hc1, irreversible line, Hc2 and distinguish among
vortex glass, vortex liquid, non-vortex states. Moreover, it can probe the
dynamic response under different frequencies and observe the threshold
phenomena of vortex liquid phase. It can even account for the density of
vortices in the vortex solid phase. Our technique is readily extended to
investigate the vortex phases in other type-II superconductors.

Superconductivity;Strongly Correlated Electrons