Perovskite multiferroics have drawn significant attention in the development of next-generation multifunctional electronic devices. However, the majority of existing multiferroics exhibit ferroelectric and ferromagnetic orderings only at low temperatures. Although interface engineering in complex oxide thin films has triggered many exotic room-temperature functionalities, the desired coupling of charge, spin, orbital and lattice degrees of freedom often imposes stringent requirements on deposition conditions, layer thickness and crystal orientation, greatly hindering their cost-effective large-scale applications. Herein, we report an interface-driven multiferroicity in low-cost and environmentally friendly bulk polycrystalline material, namely cubic BaTiO3-SrTiO3 nanocomposites which were fabricated through a simple, high-throughput solid-state reaction route. Interface reconstruction in the nanocomposites can be readily controlled by the processing conditions. Coexistence of room-temperature ferromagnetism and ferroelectricity, accompanying a robust magnetoelectric coupling in the nanocomposites, was confirmed both experimentally and theoretically. Our study explores the ‘hidden treasure at the interface’ by creating a playground in bulk perovskite oxides, enabling a broad range of applications that are challenging with thin films, such as low-power-consumption large-volume memory and magneto-optic spatial light modulator.

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Nanocrystalline Ce-substituted yttrium iron garnet (YIG) powders of different compositions, Y 3Àx Ce x Fe 5 O 12 (0 # x # 2.0), were synthesized by a combination of sol-gel auto-combustion and solid-state synthesis techniques. The as-obtained powder samples were sintered at 1150 C for 10 h. The garnet structure formation is confirmed by the X-ray diffraction pattern, which shows that the calculated lattice parameter increased for x ¼ 1.0 and shows a decreasing trend for x $ 1.0 with the addition of cerium ions. The lattice parameter increased from 12.38Å to 12.41Å for x # 1.0 whereas it decreased from 12.412Å to 12.405Å with the cerium composition for x > 1.0. The average particle size determined by high resolution transmission electron microscopy is in the range of 50 to 90 nm and found to increase with the substitution of cerium ions in YIG. The room temperature magnetic parameters such as saturation magnetization, coercivity and remanence magnetization are greatly affected by the substitution of cerium ions. The values of saturation magnetization decrease from 25.5 to 15 emu g À1 whereas coercivity increases from 1 to 28 Oe with the substitution of cerium ions. The pure YIG sample shows polycrystalline nature that changed towards a single-crystal structure leading to a preferred-(100) orientation with the Ce substitution. The change from a ring to a spotty pattern observed in SAED confirmed the crystalline phase transformation and is well supported by HRTEM and magnetic measurements. The behavior of magnetic and electrical properties is well supported by the poly-and single-crystalline nature of YIG and Ce-YIG, respectively. The crystal structure transformation in YIG brought about by Ce substitution could unveil enormous opportunities in the preparation of singlecrystal materials from their polycrystalline counterparts.

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The Ni 0.4 Cu 0.2 Zn 0.4 ferrites with different concentrations of Cr 3+ were synthesized at a low temperature (450°C) using sol-gel auto-combustion method. The X-ray diffraction analysis of the samples confirms the formation of a single-phase cubic spinel structure. The lattice constant decreases from 8.331 to 8.253 Å with an increase in Cr 3+ substitution. Bulk density decreases from 4.95 to 4.71 gm/cm 3 whereas porosity increases from 9.34% to 14.76% with an increase in Cr 3+ substitution. Transmission electron microscopy was adopted to determine the particle size. Particle size decreases from 19 to 13 nm with the addition of Cr 3+ ions. Saturation magnetization, coercivity, and other hysteresis parameters were measured using a vibrating sample magnetometer at room temperature with a maximum magnetic field of 8 kOe. Magnetization decreases from 62 to 48 emu/g, whereas coercivity increases from 65 to 180 Oe. The direct current (DC) resistivity increases from 3.62 × 10 6 to 4.21 × 10 6 Ω cm with Cr 3+ content x. The dielectric constant (ε 0 ) decreases with increasing concentration of Cr 3+ ions.

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