Abstract
The use of voltages to control magnetisation via the inverse magnetostriction effect in piezoelectric/ferromagnet heterostructures holds promise for ultra-low energy information storage technologies. Epitaxial galfenol, an alloy of iron and gallium, has been shown to be a highly suitable material for such devices because it possesses biaxial anisotropy and large magnetostriction. Here we experimentally investigate the properties of galfenol/spacer/galfenol structures in which the compositions of the galfenol layers are varied in order to produce different strengths of the magnetic anisotropy and magnetostriction constants. Based upon these layers, we propose and simulate the operation of an information storage device that can operate as an energy efficient multilevel memory cell.
Highlights
The use of voltages to control magnetisation via the inverse magnetostriction effect in piezoelectric/ ferromagnet heterostructures holds promise for ultra-low energy information storage technologies
One route is to couple the electric field to the magnetisation in a hybrid piezoelectric/magnetic structure, whereby the electric field induces a mechanical strain that is transmitted to the magnetic element, modifying the magnetic anisotropy through inverse magnetostriction, which causes the orientation of the magnetisation to switch6–11
We demonstrate experimentally how the application of a voltage to the piezoelectric layer generates a mechanical strain that modifies the magnetic anisotropy of the two galfenol layers by different magnitudes
Summary
This concept for information storage, which can be extended to multiple magnetic layers, is similar to the magnetic abacus proposed by Zhang et al., except that here we use the planar Hall effect for read out and the write operation is carried out using voltage-induced strain instead of magnetic field or current induced torque. It has been calculated that with surface electrodes patterned on the sub-μm scale, the same strain could be generated with the application of less than 1V and the energy cost of applying the voltage pulses would be on the order of a few aJ This should be compared with the fJ operation of modern MRAM operated using spin www.nature.com/scientificreports transfer torque, demonstrating the potential for hybrid piezoelectric/magnetic stacks to enable the design of high density, ultra-energy efficient information storage devices. We propose and simulate the operating characteristics of an energy efficient multilevel memory cell based on a magnetoelastic layer stack
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