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Spectral signatures of spin–phonon and electron–phonon interactions in multiferroic iron borates
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Studies of Multiferroic Palladium Perovskites
Abstract We have studied the atomic force microscopy (AFM), X-ray Bragg reflections, X-ray absorption spectra (XAS) of the Pd L-edge, Scanning electron microscopey (SEM) and Raman spectra, and direct magnetoelectric tensor of Pd-substituted lead titanate and lead zirconate-titanate. A primary aim is to determine the percentage of Pd +4 and Pd +2 substitutional at the Ti-sites (we find that it is almost fully substitutional). The atomic force microscopy data uniquely reveal a surprise: both threefold vertical (polarized out-of-plane) and fourfold in-plane domain vertices. This is discussed in terms of the general rules for Voronoi patterns (Dirichlet tessellations) in two and three dimensions. At high pressures Raman soft modes are observed, as in pure lead titanate, and X-ray diffraction (XRD) indicates a nearly second-order displacive phase transition. However, two or three transitions are involved: First, there are anomalies in c/a ratio and Raman spectra at low pressures (P = 1 − 2 GPa); and second, the c/a ratio reaches unity at ca. P = 10 GPa, where a monoclinic (M c ) but metrically cubic transition occurs from the ambient tetragonal P4 mm structure in pure PbTiO 3 ; whereas the Raman lines (forbidden in the cubic phase) remain until ca. 17 GPa, where a monoclinic-cubic transition is known in lead titanate.
Pressure-induced transition in the multiferroic CoCr[subscript 2]O[subscript 4] spinel
Abstract not provided
Visualizing weak ferromagnetic domains in multiferroic hexagonal ferrite thin film
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Palladium-based ferroelectrics and multiferroics: Theory and experiment
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High-pressure spectroscopic investigation of multiferroic Ni3TeO6
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Real-space magnetic imaging of the multiferroic spinels MnV 2 O 4 and Mn 3 O 4
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Giant pressure-enhancement of multiferroicity in CuBr[subscript 2]
Abstract not provided
Multiferroicity in atomic van der Waals heterostructures
Materials that are simultaneously ferromagnetic and ferroelectric - multiferroics - promise the control of disparate ferroic orders, leading to technological advances in microwave magnetoelectric applications and next generation of spintronics. Single-phase multiferroics are challenged by the opposite d -orbital occupations imposed by the two ferroics, and heterogeneous nanocomposite multiferroics demand ingredients' structural compatibility with the resultant multiferroicity exclusively at inter-materials boundaries. Here we propose the two-dimensional heterostructure multiferroics by stacking up atomic layers of ferromagnetic Cr 2 Ge 2 Te 6 and ferroelectric In 2 Se 3 , thereby leading to all-atomic multiferroicity. Through first-principles density functional theory calculations, we find as In 2 Se 3 reverses its polarization, the magnetism of Cr 2 Ge 2 Te 6 is switched, and correspondingly In 2 Se 3 becomes a switchable magnetic semiconductor due to proximity effect. This unprecedented multiferroic duality (i.e., switchable ferromagnet and switchable magnetic semiconductor) enables both layers for logic applications. Van der Waals heterostructure multiferroics open the door for exploring the low-dimensional magnetoelectric physics and spintronic applications based on artificial superlattices.
Nanoscale analysis of dispersive ferroelectric domains in bulk of hexagonal multiferroic ceramics
Highlights: • Aberration corrected STEM is used to link ferroelectric properties of vacancy doped multiferroic LuMnO3 ceramics to lattice defects. • Nano-scale perturbation in lattice or chemistry provokes polarization switching or phase shift of ferroelectric domains. • Partial edge dislocations modify rule of 6 in topologically protected 6-fold vortices in hexagonal RMnO3 ceramics. • Chemistry shift/lattice distortions modify ferroelectric properties, domain size and polarization switching in multiferroic. • Change in ferroelectric properties results in modification of magnetic properties in magnetoelectric h-RMnO3 multiferroic. - Abstract: The atomic nature of topologically protected ferroelectric (FE) walls in hexagonal ReMnO{sub 3} oxides (R: Sc, Y, Er, Ho, Yb, Lu) creates an interesting playground to study effects of defects on domain walls. The 6-fold FE vortices in this multiferroic family lose the ordering by the rule of 6 in the presence of partial edge dislocations (PED) besides it can be modified by chemical doping. Therefore, it is essential to comprehend the cross coupling of FE walls and defects or vacancies in the lattice of multiferroics. Atomic resolution STEM is used to explore the correlative response of electrical polarization of FE domains in the presence of defects in multiferroic ceramics. Such level of resolution also allows the study of switching of FE domains on encounter of lattice defects. The driving force behind appearance of dispersed, small FE domains in images of piezo force microscopy is revealed by observation of lattice defects and FE boundaries simultaneously at the nano-scale. Planar defects and FE domain walls play their role of internal interfaces consequently such interplaying duly modifies the magnetic and FE properties of multiferroic oxides.
Discovery of a layered multiferroic compound Cu 1-x Mn 1+y SiTe 3 with strong magnetoelectric coupling
Multiferroic materials host both ferroelectricity and magnetism, offering potential for magnetic memory and spin transistor applications. Here, we report a multiferroic chalcogenide semiconductor Cu 1-x Mn 1+y SiTe 3 (0.04 ≤ x ≤ 0.26; 0.03 ≤ y ≤ 0.15), which crystallizes in a polar monoclinic structure (Pm space group). It exhibits a canted antiferromagnetic state below 35 kelvin, with magnetic hysteresis and remanent magnetization under 15 kelvin. We demonstrate multiferroicity and strong magnetoelectric coupling through magnetodielectric and magnetocurrent measurements. At 10 kelvin, the magnetically induced electric polarization reaches ~0.8 microcoulombs per square centimeter, comparable to the highest value in oxide multiferroics. We also observe possible room-temperature ferroelectricity. Given that multiferroicity is very rare among transition metal chalcogenides, our finding sets up a unique materials platform for designing multiferroic chalcogenides.
Structural, electrical and multiferroic properties of La-doped mullite Bi{sub 2}Fe{sub 4}O{sub 9} thin films
Highlights: • Chemical solution deposited La-doped Bi{sub 2}Fe{sub 4}O{sub 9} thin film. • Structural, electrical and multiferroic properties were investigated. • La-doped Bi{sub 2}Fe{sub 4}O{sub 9} exhibited enhanced electrical and multiferroic properties. - Abstract: Thin films of (Bi{sub 2−x}La{sub x})Fe{sub 4}O{sub 9} (x = 0 and x = 0.05) were prepared on Pt(1 1 1)/Ti/SiO{sub 2}/Si(1 0 0) substrates by using a chemical solution deposition method to investigate structural, microstructural, electrical and multiferroic properties. Both the thin films were crystallized in mullite type phases with orthorhombic structures containing no secondary and impurity phases, which was confirmed by X-ray diffraction and Raman spectroscopy studies. The (Bi{sub 1.95}La{sub 0.05})Fe{sub 4}O{sub 9} thin film exhibited improved electrical and multiferroic properties at room-temperature. The leakage current density of the (Bi{sub 1.95}La{sub 0.05})Fe{sub 4}O{sub 9} thin film was one order of magnitude lower than that of the Bi{sub 2}Fe{sub 4}O{sub 9} thin film. Furthermore, in the thin film form, (Bi{sub 2−x}La{sub x})Fe{sub 4}O{sub 9} exhibited better stability against electrical breakdowns and enhanced multiferroic properties.
Multiferroic oxide thin films and heterostructures
Multiferroic materials promise a tantalizing perspective of novel applications in next-generation electronic, memory, and energy harvesting technologies, and at the same time they also represent a grand scientific challenge on understanding complex solid state systems with strong correlations between multiple degrees of freedom. In this review, we highlight the opportunities and obstacles in growing multiferroic thin films with chemical and structural integrity and integrating them in functional devices. Besides the magnetoelectric effect, multiferroics exhibit excellent resistant switching and photovoltaic properties, and there are plenty opportunities for them to integrate with other ferromagnetic and superconducting materials. The challenges include, but not limited, defect-related leakage in thin films, weak magnetism, and poor control on interface coupling. Although our focuses are Bi-based perovskites and rare earth manganites, the insights are also applicable to other multiferroic materials. We will also review some examples of multiferroic applications in spintronics, memory, and photovoltaic devices.