Novel magnetostrictive memory device

Abstract

A stress-operated memory device consisting of an ellipsoidal magnetic particle array and an electrostrictive grid is proposed. In the device, the magnetic state of the particle can be controlled only by the magnetostriction effect. Each particle is located at the intersection of the grid and has an in-plane uniaxial anisotropy. A pair of electric contacts is connected to the end of each wire. In the writing process, the driving voltages are simultaneously applied to two pairs of the selected contacts. This allows to apply a local electric field whose direction and amplitude can be regulated by varying the voltage intensity and polarity. The exerting stress on the magnetic particle results in the linear magnetostriction and hence an additional anisotropy energy in the particle. The in-plane total energy minimum, corresponding to the magnetization direction, follows the local electric field. Consequently the magnetization of the single magnetic particle located at the intersection can therefore be selectively switched.

Non-volatile electrically-driven repeatable magnetization reversal with no applied magnetic field

“…Demonstrating electrical control of coercivity 19,24 , exchange bias 25,26 or magnetic anisotropy 20,27 is insufficient because, respectively, an electrically addressable coercivity is inextricably linked with an applied magnetic field; because exchange bias is an interfacial phenomenon that cannot readily drive magnetization reversal throughout a film of significant thickness; and because no new magnetic anisotropy axis can lie more than 901 from the anisotropy axis along which the local magnetization initially lies. It has been suggested that this latter challenge may be overcome by applying a suitable sequence of normal stresses near the pre-existing magnetic anisotropy axes of a small homogeneously magnetized Stoner-Wohlfarth particle 28,29 , but this has not been experimentally realised.…”

Understanding and designing magnetoelectric heterostructures guided by computation: progresses, remaining questions, and perspectives

“…7b). Compared to previous schemes, 136,137 these geometrical design based schemes enable greater design flexibility such as a wider range of materials selection and readily tunable angle between the applied piezostrain and the pre-exiting magnetic easy axes.…”

“…It has been theoretically demonstrated that applying a suitable sequence of uniaxial normal strain near the pre-existing magnetic easy axis of a singledomain magnet can rotate the magnetization vector in a deterministic manner and achieve a 180°magnetization switching. 136,137 However, these proposals rely on the use of either a rotating piezostrain, 136 or a single-crystal magnet that shows two mutually perpendicular magnetic easy axes due to a four-fold magnetocrystalline anisotropy. 137 Recently, it has been shown that two pre-existing and mutually perpendicular magnetic easy axes can also appear in a flower-shaped magnetic nanodot with a fourfold shape anisotropy, 138 or in a square-shaped magnetic nanodot 139 with a four-fold magnetic configurational anisotropy 140 (see schematic in Fig.…”

GaMnAs-based hybrid multiferroic memory device

“…Alternatively, magnetoelectric coupling can be indirectly introduced between ferromagnetic and ferroelectric materials via strain, and in this case, the ferromagnetic material can be conducting. A conceptual memory device made of ferromagnetic and piezoelectric materials has been proposed, 10 and permeability changes in magnetostrictive films, 11 changes in coercive field, 12 and reorientation of the easy axis from in plane to out of plane in Pd/ CoPd/ Pd trilayers 13 have recently been demonstrated.…”