Controlling Magnetic Properties of Epitaxial Nanocomposite Thin Films Through Ionic Liquid Gating

Author / Creator

MMM 2020 (2020)

Conferences

MMM 2020 P5: Multiferroic Materials and Hetero-Structures II (2020)

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Online

Summary

Voltage control of the structure, magnetic and electronic properties of materials enables the realization of new types of nonvolatile magnetoelectric memory devices. Here, we investigate the effect...

Voltage control of the structure, magnetic and electronic properties of materials enables the realization of new types of nonvolatile magnetoelectric memory devices. Here, we investigate the effect of ionic liquid gating on the magnetic properties of self-assembled heterostructure films consisting of nanoscale CoyFe3-yO4 (CFO) spinel pillars embedded in a SrCo1-xFexO3-δ (SCFO) perovskite (P) or brownmillerite (BM) matrix, over a range of compositions x and y. These self-assembled nanocomposites are grown by pulsed laser deposition on SrTiO3 substrates using SrCoO3-δ-SrFeO3-δ, SrCoO3-δ-Fe3O4, or SrFeO3-δ-Co3O4 pairs of targets. We first describe the growth kinetics of these nanocomposites, focusing on how the oxygen pressure affects the distribution of Co and Fe between the two phases and the formation of P vs. BM structure for the matrix. Unusually, at high oxygen pressures, the two-phase structure can grow from the codeposition of SrCoO3-δ and SrFeO3-δ, attributed to depletion of the Sr in the film. The pillar CFO magnetism depends on y, e.g. ferrimagnetic with room temperature saturation magnetization Ms ~300 kA/m for y=1 and paramagnetic for y=0. The matrix SCFO with the BM phase has antiferromagnetic ordering irrespective of x, while the magnetism of the P phase depends strongly on x and can exhibit a room temperature Ms ~100 kA/m for x=0.5 but almost no moment for x=0 and x=1 [1]. With the gating voltage of -3V/+3V, the lattice parameter of matrix SCFO changes ±3% and induces strain transfer around ±1% to the pillar phase (Fig. 1). In particular, for x=0.5 and y=0 (Fig. 2), the negative gating inserts oxygens into the BM phase and changes it into a P phase showing ferromagnetism. Our study clarifies the manipulation of the magnetism of composite materials through an electrochemical process, expanding the applications of magnetoelectric coupling.References: [1] S. Ning, Q. Zhang and C. A. Ross, ACS Nano, https://dx.doi.org/10.1021/acsnano.0c03750 (2020)

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