60 ∘ and 120 ∘ domain walls in epitaxial BaTiO 3 (111)/Co multiferroic heterostructures
Not Available
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
SEARCH · Engineering Papers
Results for “multiferroics”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Spin dynamics in natural multiferroic pyroxene NaFeSi 2 O 6
Spin dynamics in the natural mineral aegirine, NaFeSi 2 O 6 , a member of the pyroxene family, was studied by elastic and inelastic neutron scattering. Magnetization and specific-heat measurements as well as single-crystal neutron diffraction maps, taken in the temperature range 2–20 K, confirm two successive magnetic transitions at 8.8 and 5.8 K, consistent with previous studies. The observed spin-wave excitations emerge from the incommensurate magnetic Bragg peaks corresponding to the propagation vector 𝑘 ICM = (0,0.77,0), and extend up to energies of about 1.5 meV. In the low-temperature helical phase, the spin dynamics of the Fe3+ ions is well described by a simple linear spin-wave model. The observed excitations can be modeled using a spin Hamiltonian that includes three primary exchange interactions—intrachain coupling 𝐽 = 0.142(2) meV, and interchain couplings 𝐽 1 = 0.083(1) meV and 𝐽 2 = 0.186(1) meV—and an easy-plane anisotropy 𝐷 = 0.020(6) meV. Furthermore, our results show that no single exchange interaction dominates the spin dynamics. The similar strengths of the intrachain and interchain couplings point to the fact that the magnetic interactions in aegirine are three dimensional rather than confined along one direction. As a result, the system cannot be considered quasi one dimensional, as previously suggested, and calls for further investigations.
Magnetic coupling↗
POLYMERIC MULTIFERROIC, COLLABORATIVE RESEARCH BETWEEN UNIVERSITY OF MARYLAND AND KANSAS UNIVERSITY
The research was directed towards finding new functional materials, mainly polymeric. Main accomplishment consisit of indentifying mulktiferroic polymers and a shape memory alloy featuring an ultralong fatigue life of 10 million cycles.
36 MATERIALS SCIENCE↗
High P-T Raman study of transitions in relaxor multiferroic Pb(Fe 0.5 Nb 0.5 )O 3
The vibrational and structural properties of Pb(Fe 0.5 Nb 0.5 )O 3 have been investigated using Raman spectroscopy up to 40 GPa at 300 K and from 300 to 415 K at selected pressures. The measurements reveal three phase transitions at 5.5, 8.7 and 24 GPa at room temperature. The temperature dependences of the spectra indicated transitions at 1.5 GPa, at 335 and 365 K. The results support the appearance of an intermediate tetragonal P 4mm phase between ferroelectric R 3m and paraelectric P m-3m phases. Furthermore, a P-T phase diagram is proposed that allows further insight into the magnetoelectric coupling present in this material.
36 MATERIALS SCIENCE↗
Multiferroic and Related Hysteretic Behavior in Ferromagnetic Shape Memory Alloys
In this work, we combine a Ginzburg–Landau model for a ferroelastic transition with the theory of micromagnetism to study the magnetostructural behavior leading to multicaloric effects in ferromagnetic shape memory alloys. We analyze the ferroelastic transition under different conditions of temperature, stress and magnetic field and establish the corresponding phase diagram. On the one hand, our results show that the proper combination of both fields may be used to reduce the transition hysteresis and thus improve the reversibility of the related elastocaloric effects, superelasticity and stress-mediated magnetocaloric effects. On the other hand, the stress-free magnetic field-driven and thermally driven magnetostructural evolution provides physical insight into the low-temperature field-induced domain reorientation, from which we derive strategies to modify the operational temperature ranges and thus the corresponding (magnetic) shape-memory effect.
36 MATERIALS SCIENCE↗
Elastic and anelastic relaxation behaviour of perovskite multiferroics II: PbZr0.53Ti0.47O3 (PZT)–PbFe0.5Ta0.5O3 (PFT)
Not provided.
Materials Science↗
Effect of Mo Doping at the B Site on Structural and Electrical Properties of Multiferroic BiFeO{sub 3}
The Mo-doped BiFe{sub 1−x}Mo{sub x}O{sub 3}, where x = 0 and 0.6, samples were synthesised by the solid-state reaction method. Admirable ferroelectric and piezoelectric properties are expected on substituting solid solutions of bulk BFO with other oxide perovskite compounds. It offers an alternative and is an environment-friendly candidate for lead-free ferroelectric and piezoelectric devices. The prepared samples were investigated by XRD, Fourier transform infrared spectroscopy (FTIR), current density (JE) measurement, PE loop tracer and field emission scanning electron microscopy to examine their crystal structure, bonding nature, current density, ferroelectric hysteresis loop and surface morphology. The Mo-doped BFO shows a change in structure, increased grain size, reduction in current density and enhancement in the PE loop on doping Mo at the Fe site.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Effect of Nd Substitution on Properties of Multiferroic Bismuth Ferrite Synthesized by Sol-Gel Auto-combustion Method
In this work, pure and Nd-doped bismuth ferrite nanocrystals with the general formula of Bi{sub 1−x}Nd{sub x}FeO{sub 3} (x = 0, 0.05, 0.1, 0.15, 0.2) were synthesized via the sol-gel auto-combustion method at two different calcination temperatures (550 and 650{sup ∘}C). Phase analysis and investigating structural, thermal, and magnetic properties and measuring the size of nanoparticles have been done by using X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric and differential thermal analysis (TG/DTA), and vibrating sample magnetometry (VSM). For undoped BiFeO{sub 3} (BFO), increasing calcination temperature will increase the average size of nanocrystals. On the other hand, the average size of nanoparticles is decreased by increasing the concentration of neodymium in the structure of BFO. By entering neodymium to the structure of bismuth ferrite at the calcination temperature of 550{sup ∘}C, the ferromagnetic properties decline. However, at 650{sup ∘}C, ferromagnetic properties are improved which is due to a fall in the number of Fe{sup 2+} ions. In this case, by decreasing the Fe{sup 2+} ions, remanent and saturation magnetization increase.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Substrate-Dependent Structure, Magnetic, and Ferroelectric Properties of Multiferroic Bi{sub 0.9}Ba{sub 0.1}FeO{sub 3} Thin Film
The structure characteristic of substrate is a key parameter to modify the structure of as-grown thin film and tune physical properties for oxide thin film materials. Three various substrates are selected to identify the change of structure as well as ferroelectric and magnetic properties of the fabricated Bi{sub 0.9}Ba{sub 0.1}FeO{sub 3} thin film. XRD and TEM combined with AFM were used to confirm the detailed structure and epitaxial growth of Bi{sub 0.9}Ba{sub 0.1}FeO{sub 3} thin film on different substrates. Correspondingly, the changes of the ferroelectric and magnetic properties were investigated. It is found that the lattice mismatch between substrate and thin film significantly promotes the structure distortion of Bi{sub 0.9}Ba{sub 0.1}FeO{sub 3} thin film inducing the change of ferroelectric and magnetic properties. Our results further reveal that the structure characteristic of substrate plays a major role in determining the structure of epitaxial thin film and the enhancement of physical properties, which sheds light to understanding the effect of lattice mismatch in many other functional oxide thin films as well.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Ferroelasticity in a metal-organic framework perovskite; towards a new class of multiferroics
A metal–organic framework perovskite, [(CH 2 ) 3 NH 2 ][Mn(HCOO) 3 ], exhibits a weakly first order ferroelastic phase transition at ~272 K, from orthorhombic Pnma to monoclinic P2 1 /n, and a further transition associated with antiferromagnetic ordering at ~8.5 K. The main structural changes, through the phase transition, are orientational ordering of the azetidium groups and associated changes in hydrogen bonding. In marked contrast to conventional improper ferroelastic oxide perovskites, the driving mechanism is associated with the X-point of the cubic Brillouin zone rather than being driven by R- and M-point octahedral tilting. The total ferroelastic shear strain of up to ~5% is substantially greater than found for typical oxide perovskites, and highlights the potential of the flexible framework to undergo large relaxations in response to local structural changes. Measurements of elastic and anelastic properties by resonant ultrasound spectroscopy show some of the characteristic features of ferroelastic materials. In particular, acoustic dissipation below the transition point can be understood in terms of mobility of twin walls under the influence of external stress with relaxation times on the order of ~10 -7 s. Elastic softening as the transition is approached from above is interpreted in terms of coupling between acoustic modes and dynamic local ordering of the azetidium groups. Subsequent stiffening with further temperature reduction is interpreted in terms of classical strain–order parameter coupling at an improper ferroelastic transition which is close to being tricritical. By way of contrast, there are no overt changes in elastic or anelastic properties near 9 K, implying that any coupling of the antiferromagnetic order parameter with strain is weak or negligible.
Li, Wei↗
Magnetic structure of magnetoelectric multiferroic HoFeWO 6
The polar magnetic oxide, HoFeWO6, is synthesized, and its crystal structure, magnetic structure, and thermodynamic properties are investigated. HoFeWO 6 forms the polar crystal structure (space group Pna2 1 (#33)) due to the cation ordering of W 6+ and Fe 3+ . An antiferromagnetic transition at T N = 17 K is accompanied by a significant change in magnetic entropy with a value of ≈ 5 J kg -1 K-1 in a 70 kOe applied field. Temperature dependent neutron diffraction and magnetization data indicate that the Fe sublattice orders in a strongly non-collinear and non-coplanar arrangement below T N . The Fe ordering initially leads to induced ordering of the Ho spins such that the Ho spins also show behavior of long-range ordering that is evident from the neutron diffraction measurements. Below T ≈ 4 K, the Ho spins order independently and pull the Fe spins toward the direction of Ho spins. A comparison with the magnetic structures and corresponding ferroelectric properties of other members of RMWO 6 (R = Y, Sm-Tm, M = Cr, Fe, V) family indicate that the spontaneous polarization is due to the magnetic structure specific to the Fe sublattice through magnetoelectric coupling whereas the polarization is independent of the Ho sublattice.
36 MATERIALS SCIENCE↗
Spin-Coating and Characterization of Multiferroic MFe{sub 2}O{sub 4} (M=Co, Ni) / BaTiO{sub 3} Bilayers
Bilayer films of MFe{sub 2}O{sub 4} (M=Co, Ni) and BaTiO{sub 3} were prepared by spin coating of N,N-dimethylformamide/acetic acid solutions on platinum coated silicon wafers. Five coating steps were applied to get the desired thickness of 150 nm for both the ferrite and perovskite layer. XRD, IR and Raman spectroscopy revealed the formation of phase-pure ferrite spinels and BaTiO{sub 3}. Smooth surfaces with roughnesses in the order of 3 to 5 nm were found in AFM investigations. Saturation magnetization of 347 emu cm{sup −3} for the CoFe{sub 2}O{sub 4}/BaTiO{sub 3} and 188 emu cm{sup −3} for the NiFe{sub 2}O{sub 4}/BaTiO{sub 3} bilayer, respectively were found. For the CoFe{sub 2}O{sub 4}/BaTiO{sub 3} bilayer a strong magnetic anisotropy was observed with coercivity fields of 5.1 kOe and 3.3 kOe (applied magnetic field perpendicular and parallel to film surface), while for the NiFe{sub 2}O{sub 4}/BaTiO{sub 3} bilayer this effect is less pronounced. Saturated polarization hysteresis loops prove the presence of ferroelectricity in both systems. - Graphical abstract: The SEM image of the CoFe{sub 2}O{sub 4}/BaTiO{sub 3} bilayer on Pt–Si-substrate (left), magnetization as a function of the magnetic field perpendicular and parallel to the film plane (right top) and P–E and I–V hysteresis loops of the bilayer at room temperature. - Highlights: • Ferrite and perovskite oxides grown on platinum using spin coating technique. • Columnar growth of cobalt ferrite particle on the substrate. • Surface investigation showed a homogenous and smooth surface. • Perpendicular and parallel applied magnetic field revealed a magnetic anisotropy. • Switching peaks and saturated P–E hysteresis loops show ferroelectricity.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Charge ordering and multiferroicity in Fe{sub 3}BO{sub 5} and Fe{sub 2}MnBO{sub 5} oxyborates
The comparison of Fe{sub 3}BO{sub 5} and Fe{sub 2}MnBO{sub 5} reveals that the 2Fe{sup 2+}: Fe{sup 3+} charge ordering of the former is suppressed in the latter. Spin dynamics probed by ac susceptibility are strongly affected by the substitution, inducing superparamagnetism at low temperature in Fe{sub 2}MnBO{sub 5}. Interestingly, for both oxyborates, glassiness is observed in the dielectric properties at low temperature, but only Fe{sub 3}BO{sub 5} shows a magnetodielectric effect close to its lower magnetic transition. A change in the electrical polarization, measured by pyroelectric current integration, is observed in Fe{sub 3}BO{sub 5} and is even more pronounced in Fe{sub 2}MnBO{sub 5}. Such results suggest that these oxyborates behave like antiferromagnetic relaxor ferroelectrics. These features are proposed to be related to the distribution of the species (Fe{sup 3+}, Fe{sup 2+} and Mn{sup 2+}) over the four transition metal sites forming the ludwigite structure. - Graphical abstract: 90 K [010] electron diffraction patterns of Fe{sub 3}BO{sub 5}. The yellow arrows in the pattern indicate the extra-spots corresponding to the superstructure induced by the charge ordering. - Highlights: • The TEM (ED) study of the Fe{sub 3}BO{sub 5} oxyborate at 90 K reveals a superstructure related to a Fe{sup 2+}/Fe{sup 3+} ordering. • The Fe{sub 2}MnBO{sub 5}, Mn-substituted counterpart, does not show such ordering. • Our magnetic and electric measurements demonstrate that these magnetic ferrites exhibit glassiness in their charges (relaxor-type) with additional superparamagnetism at low T for Fe{sub 2}MnBO{sub 5} and magnetodielectric coupling near T{sub N2}=72 K in Fe{sub 3}BO{sub 5}. • The pyroelectric measurements confirm the existence of a ferroelectric behavior in these antiferromagnets. Accordingly, our results open the route to the study of other large class of the M{sub 2}{sup 2+}M’{sup 3+}BO{sub 5} ludwigites and to their complex magnetism and its relationship to relaxor ferroelectricity.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Structural, electrical and magnetic properties of Bi{sub 0.825}Pb{sub 0.175}FeO{sub 3}, and Bi{sub 0.725}La{sub 0.1}Pb{sub 0.175}FeO{sub 3} multiferroics
Graphical abstract: - Highlights: • Samples synthesized by solid state reaction route successfully. • La and Pb substitutions significantly change the BiFeO{sub 3} crystal symmetry. • The presence of E(TO9) and E(LO9) modes indicates ferroelectric domain of BiFeO{sub 3}. • Doped ions and crystal structure affect the dielectric properties of the samples. • The observed value of conductivity for BPFO sample is 3.1 × 10{sup −9} σ{sup −1} cm{sup −1}. - Abstract: Single-phase BiFeO{sub 3}, Bi{sub 0.825}Pb{sub 0.175}FeO{sub 3} and Bi{sub 0.725}La{sub 0.1}Pb{sub 0.175}FeO{sub 3} ceramic samples were prepared via solid state reaction route to study the effects of co-doping (La/Pb) on their crystal structure and ferroelectromagnetic behaviour. X-ray diffraction data accompanied by Rietveld refinement showed that BiFeO{sub 3} crystallize in rhombohedral distorted perovskite structure (space group-R3c) while to that BPFO and BLPFO crystallize in tetragonal (P4/mmm) symmetry. Presence of E(TO9) and E(LO9) modes in Raman scattering spectra for BiFeO{sub 3} and Bi{sub 0.725}La{sub 0.1}Pb{sub 0.175}FeO{sub 3} infers ferroelectric nature. However, absence of both modes in Bi{sub 0.875}Pb{sub 0.175}FeO{sub 3} indicates the paraelectric nature. The room temperature dielectric constant (10 Hz–1 MHz) of BiFeO{sub 3}, Bi{sub 0.825}Pb{sub 0.175}FeO{sub 3} and Bi{sub 0.725}La{sub 0.1}Pb{sub 0.175}FeO{sub 3} is about 100, 60, and 200. Ferroelectromagnetic measurements revealed the existence of ferroelectricity with remnant polarization of 0.24 μC/cm{sup 2} in Bi{sub 0.725}La{sub 0.1}Pb{sub 0.175}FeO{sub 3}, paraelectricity in Bi{sub 0.875}Pb{sub 0.175}FeO{sub 3}, and weak (strong) ferromagnetism with remnant magnetizations of 0.25 (1.57) emu/g in Bi{sub 0.725}La{sub 0.1}Pb{sub 0.175}FeO{sub 3} (Bi{sub 0.825}Pb{sub 0.175}FeO{sub 3})
36 MATERIALS SCIENCE↗
Tuning of magnetic transition temperatures in nanoparticles of CoCr{sub 2}O{sub 4} multiferroic by B-site mixing
Highlights: • Pure CoCr{sub 2−x}Fe{sub x}O{sub 4} (x = 0.1 and 0.2) nanoparticles of 16–20 and 6–10 nm show enhancement of T{sub c} from 100 to 110 K and T{sub s} from 18 K to 36 K with increasing Fe. • The theoretical variation of reciprocal susceptibility with temperature in paramagnetic region using the function χ{sup −1} = T/C + 1/χ{sub 0} – b/(T − θ) is fitted with the experimental data. • The difference in ferrimagnetic Curie point, θ{sub f} and paramagnetic Curie point, θ{sub p} is 30 K and 7 K respectively for sample x = 0.1 and 0.2 indicating a sharp ferri- to para-magnetic transition in the former one. - Abstract: Pure CoCr{sub 2−x}Fe{sub x}O{sub 4} nanoparticles synthesized through conventional coprecipitation technique show particle size distribution in the range of 16–20 and 6–10 nm for x = 0.1 and 0.2 respectively. Magnetic and specific heat measurements show an enhancement of paramagnetic to collinear ferrimagnetic transition temperature, T{sub c} from 100 to 110 K and to a short range non-collinear spiral ordering, T{sub s} from 18 to 36 K with increasing x from 0.1 to 0.2 respectively. In addition, a strong disagreement between the paramagnetic moment obtained from the fitting of χ{sup −1} = T/C + 1/χ{sub 0} – b/(T − θ) and ferrimagnetic moment measured from the M vs. H loop at 10 K corroborates the nonsaturation behavior of magnetization at 50–100 kOe field and an order of magnitude higher coercivity (H{sub c}). The enhancement of T{sub c} and T{sub s} with increasing Fe concentration is attributed to an intrinsic change in non-collinear to collinear spin structure and strong J{sub A–B} interaction.
36 MATERIALS SCIENCE↗