Four-state nanomagnetic logic using multiferroics
  The authors show how to implement a 4-state universal logic gate (NOR) using three strain-coupled magnetostrictive-piezoelectric multiferroic nanomagnets (e.g. Ni/PZT) with biaxial magnetocrystalline anisotropy. Two of the nanomagnets encode the 2-state input bits in their magnetization orientations and the third nanomagnet produces the output bit via dipole interaction with the input nanomagnets. A voltage pulse alternating between -0.2 V and +0.2 V is applied to the PZT layer of the third nanomagnet and generates alternating tensile and compressive stress in its Ni layer to produce the output bit, while dissipating ~ 57,000 kT (0.24 fJ) of energy per gate operation. 
Noel D'Souza, Jayasimha Atulasimha, and Supriyo Bandyopadhyay
cond-mat.mes-hall