  A major challenge in spin-based electronics is reducing power consumption for
magnetization switching of ferromagnets, which is being implemented by
injecting a large spin-polarized current. The alternative approach is to
control the magnetic anisotropy (MA) of the ferromagnet by an electric field.
However, the voltage-induced MA is too weak to deterministically switch the
magnetization without an assisting magnetic field, and the strategy towards
this goal remains elusive. Here, we demonstrate a new scheme of
orbital-controlled magnetization switching (OCMS): A sharp change in the MA is
induced when the Fermi level is moved between energy bands with different
orbital symmetries. Using a ferromagnetic oxide interface, we show that OCMS
can be used to achieve a deterministic and magnetic-field-free 90
degree-magnetization switching solely by applying an extremely small electric
field of 0.05 V/nm with a negligibly small current density of 10^-2 A/cm^2. Our
results highlight the huge potential of band engineering in ferromagnetic
materials for efficient magnetization control.
