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.
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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