Control of ferromagnetic properties by spontaneous polarization of various perovskite substrates ABO₃: First principles study

As the size of CMOS-based semiconductor devices decreases, various quantum mechanical limitations become serious issues to be solved. To overcome limitations, spin-based devices have been proposed. However, there are several issues in spin-based devices as well. Compared to the energy required to maintain the magnetic information, it needs 10⁵ times higher energy to switch spin states. Recently, spin-based devices demonstrated that the ferromagnetic spin states can be switched by a multiferroic material with much lower switching energy than conventional CMOS devices by a factor of 10 to 30. More recently, instead of this multiferroic material, a soft magnetic cladding structure was proposed for ferromagnetic switching. Still, the key issue is how to lower magnetic anisotropy energy enabling easier spin switching. Using first-principles density functional theory, we investigate the magnetic properties of a ferromagnetic layer, such as Fe, stacked on various ferroelectric oxides ABO₃ where A is one of the alkaline earth metals (Ca, Sr, or Ba) and B is a transition metal in the titanium group (Ti, Zr, or Hf). We explore how to utilize spontaneous polarization of ferroelectric substrates to tailor the magnetic properties including magnetic anisotropy of the ferromagnetic layer.