Fabrication Of All Thin Film Magneto-Electric Coupled Memory Devices

Abstract

We studied a novel approach to MRAM using magneto-electric (ME) coupled devices: heterostructures consisting of at least two materials, one piezoelectric, and the other magnetostrictive, that are connected by mechanical coupling. Strain in one layer is transferred to another layer due to mechanical transduction, causing a change of properties in the layer onto which the strain is applied. In converse magneto-electric coupling an applied voltage to the piezoelectric layer causes a strain change (converse piezoelectric effect) that is mechanically coupled to the magnetostrictive layer, changing its magnetic anisotropy (Villari effect). Our converse ME heterostructure consists of mechanically coupled PZT and FeGa thin films. The PZT layers acquire different strain states when an applied electric field. Mechanical transduction couples this strain to the FeGa, which then changes its magnetic anisotropy. This thesis discusses the fabrication of a converse ME memory element that is non-volatile, low power consuming, and all-thin-film.