Proving the Suitability of Polymer-Based Magnetoelectrics for Spintronic Applications

The rapid advancement of technology has generated significant requirements for electrical energy to power electronic devices. A pivotal aspect of this technological progress, for sensors, actuators, and memory devices, involves harnessing the spin of electrons in electronics, known as spintronics. However, a considerable portion of the electric power utilized in spintronics is dissipated as heat through the Joule effect ( 3–5% of the energy: thousands of millions of dollars annually). Consequently, there is a pressing need to explore novel approaches to develop energy-efficient devices, making it a prominent research topic within the realm of spintronics.<br/>To address concerns regarding energy efficiency and the control of spin states, alternatives to the energy-consuming external magnetic field have been explored: the spin-polarized current injection. However, this approach still generates heat, negatively impacting the overall power efficiency of the device. In this scope, the utilization of applied voltages represents a promising strategy to reduce energy requirements. Materials with magnetoelectric (ME) properties have emerged as leading contenders for future spintronic advancements, as their magnetization and ferromagnetism can be controlled by an electric field.<br/>By incorporating an additional magnetoelectric (ME) layer into the conventional three-layer spin-valve spintronic structure, it becomes possible to create electrically tunable spintronic devices. This is achieved by exploiting the interface between the ME layer and the ferromagnetic-free layer. The introduction of this ME layer brings about a significant reduction in power consumption, estimated to be two orders of magnitude lower when compared to traditional devices.<br/>In the broader context of the global technological landscape, which is witnessing the rapid and widespread implementation of revolutionary advancements such as Industry 4.0, the Internet of Things, and digitalization, the production of ME materials is facilitated by additive manufacturing tools. These tools not only enable the efficient manufacturing of ME materials but also ensure safety during the production process, productivity, reduced time requirements, miniaturization, and sustainability.<br/>Among the different & available ME materials, polymer-based ME materials have been specifically selected to demonstrate their suitability for spintronic applications, due to their flexibility, high ME coupling, and printability, making them ideal for integration into spintronic devices. In particular, P(VDF-TrFE) (poly(vinylidene fluoride-trifluoroethylene)) has been selected as the piezoelectric matrix material due to its exceptional piezoelectric response, which is the highest among all polymers (|d₃₃|≈30 pC/N). Three different types of magnetostrictive fillers were incorporated into the polymer matrix: CoFe₂O₄ nanoparticles, Fe₃O₄ nanoparticles, and NdFeB microparticles.<br/>Results show that an AC electric field of 10 V/f ≈ 13 MHz applied on samples with 20 wt.% of magnetic filler produced magnetic fields of ≈ 8 Oe in all three composites, that correspond to converse ME coefficients of 4.1, 4.4, and 6.5 mG.cm.V^-1, respectively for P(VDF-TrFE) composites with NdFeB, Fe₃O₄ and CoFe₂O₄ fillers. CoFe₂O₄ fillers induced the highest converse ME coefficient due to their highest magnetostriction (≈250 ppm)<br/>Such performance holds promise for spintronic (low field sensing and memory applications) once the generated magnetic fields are greater than the ones needed for recently reported spin-valve structures (0.4 Oe).