Tuning the magnetic properties of self-assembled BiFeO₃–CoFe₂O₄heteroepitaxy by magneto-structural coupling

Abstract

Magnetic and multiferroic nanocomposites with two distinct phases have been a topic of intense research for their profound potential applications in the field of spintronics. In addition to growing high-quality phase separated heteroepitaxial nanocomposites, the strain engineering that is conducive to enhance the tunability of material properties, in general, and the magnetic properties, in particular, is of utmost importance in exploring new possibilities. Here, we investigated the magneto-structural coupling between antiferromagnetic BiFeO3 (BFO) and ferrimagnetic CoFe2O4 (CFO) in self-assembled vertically aligned nanocomposites grown on LaAlO3 (LAO) and SrTiO3 (STO) substrates. We found that BFO exhibits tetragonal (T) and rhombohedral (R) structures as the stable phases and CFO has high magnetocrystalline anisotropy even in the form of nanocomposites. The temperature and magnetic field dependent magnetizations of T_BFO-CFO/LAO and R_BFO-CFO/STO nanocomposites primarily demonstrate the magnetoelastic coupling between these variants.

Flexible Multiferroic Bulk Heterojunction with Giant Magnetoelectric Coupling via van der Waals Epitaxy

“…The calculated longitudinal and transverse magnetostriction coefficients are -51 ppm and 61 ppm, respectively (with ∆ = ∥ − ⊥ = -112 ppm), slightly higher than that of CFO/mica (∆λ = -104 ppm), 20 which can be attributed to the strong antiferromagnetic-ferrimagnetic coupling of BFO-CFO. 8,40 This result is also in agreement with the previous reports that CFO has negative longitudinal magnetostriction and positive transverse magnetostriction. 1,25 Magnetoelectric with the applied magnetic field from 76.5 pmV -1 to 42.5 pmV -1 as shown in Figure 4a.…”

Formation and physical properties of the self-assembled BFO–CFO vertically aligned nanocomposite on a CFO-buffered two-dimensional flexible mica substrate

“…Hence, one may wet the substrate completely, resulting in a layer-by-layer growth mode to form as the matrix, while the other only wets the substrate partially and an island growth mode prevails to form as pillars. [14][15][16]18,20,21,25 In most cases, one expects that the selfassembled growth can only occur when the rigid perovskite substrate being used owing to the necessity of achieving a cubicto-cubic relation between constituent phases and substrates. [14][15][16]24 In contrast, since the mica substrate is having a monoclinic crystal structure with a ¼ 0.5199 nm, b ¼ 0.9027 nm, c ¼ 2.0106 nm, and space group of C2/c, apparently it is impossible to meet the requirement of cubic-to-cubic relation between constituent phases and substrates.…”

“…[14][15][16] The present work reports the detailed mechanisms leading to the self-assembled heteroepitaxial growth of the threedimensional (3D) BiFeO 3 -CoFe 2 O 4 (BFO-CFO) VAN on exible mica substrate. Previously, the BFO-CFO VAN grown on various rigid ceramic substrates has been illustrated as multiferroic nanocomposite exhibiting strong magnetoelectric coupling effects, [17][18][19][20] which can bring about profound application potential for next-generation electronic devices in elds such as memory, magnetic sensor, and energy harvesting. It has been recognized that the matrix-pillars conguration of the BFO-CFO VAN was enabled mainly via the surface energy difference between the interface of substrate/perovskite-structured BFO and substrate/spinel-structured CFO.…”

“…15,16 Consequently, the fabrication of the BFO-CFO VAN system has been stringently limited by the strict requirements of compatible lattice matching and cubic-to-cubic orientation relationships among the two constituent phases and the substrates. 14,18,[20][21][22] When the lattice mismatch between either constituent phase and the substrate is too large, substantial amount of dislocations and defects are oen observed within the resultant lms. 21 Since the mica is 2D material, how the self-assembled BFO-CFO VAN thin-lm grown on mica can still lead to highly crystalline epitaxial growth characteristic is interesting by itself.…”

Structure, Ferroelectricity, and Magnetism in Self‐Assembled BiFeO3–CoFe2O4 Nanocomposites on (110)‐LaAlO3 Substrates

“…They can exhibit strong magnetoelectric coupling and may be useful in magnetoelectric memory or logic devices . The strain state and the crystal structure of BFO in both single‐phase films and nanocomposites can be modified by changing the substrate lattice parameter or the film thickness . BFO films grown with a small in‐plane compressive strain, e.g., on SrTiO 3 , form a rhombohedral crystal structure with a small monoclinic distortion.…”