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Hydrogen molecules adsorption and storage in Sc coated Si@Al12 cluster were investigated using density functional theory methods. Scandium atoms can bind strongly to the surfaces of Si@Al12 due to the charge transfer between Sc and Si@Al12, and do not suffer from clustering on the substrate. Si@Al12 cluster coated with three and four Sc atoms can adsorb 16 and 18 H2 molecules with a binding energy of 0.28–0.63 eV/H2, corresponding to hydrogen storage capacity of 6.0 and 6.3 wt %, respectively. The stable Si@Al12 can be applied as one of candidates for hydrogen storage materials at ambient conditions. [ABSTRACT FROM AUTHOR]

Rare-earth titanate cubic pyrochlore Ho2Ti2O7 ceramics are prepared by the standard solid state reaction. The magnetic, dielectric, and ferroelectric behaviors are measured in order to investigate the multiferroic behaviors of Ho2Ti2O7. Upon the gradual spin ordering sequence with decreasing temperature, a ferroelectric transition with a small polarization is identified. We discuss the origin of ferroelectricity and its possible correlation with the spin order at low temperature. [ABSTRACT FROM AUTHOR]

The studies on the structure and electronic properties of hydrogenated metal embedded Al12 cage clusters have been performed by density functional theory calculations. We have investigated aluminum cluster hydrides with 12 and 14 hydrogen atoms, respectively. Insertion of the Mg, Ca alkali metals remarkably enhances the stability of the aluminum clusters. The hydrogen atom prefers to occupy on-top sites along the surface of the clusters. Mulliken population analysis indicates that significant charge transfer occurs between the Mg and Ca atoms and the Al atoms. Our computations suggest that these clusters appear to be physically and chemically stable. [ABSTRACT FROM AUTHOR]

Bi5Ti3FeO15 bulk ceramic and thin film samples are prepared using the sol-gel method. The dielectric, ferroelectric, and magnetic behaviors of these samples are measured in order to investigate the possible multiferroic effect. The superparamagnetic behavior with dominant antiferromagnetic (AFM) interaction background for the as-prepared Bi5Ti3FeO15 samples is revealed. The clearly identified magnetocapacitance effect at low temperature is argued to originate from the suppression of the AFM interaction by external magnetic field. [ABSTRACT FROM AUTHOR]

Magnetoelectric (ME) Pb(Zr0.52Ti0.48)O3 (PZT)–NiFe2O4 bulk composites with various PZT volume fractions were prepared. The ME coupling coefficient, impedance, and flux density versus the frequency were measured. The magnetic bias and PZT volume fraction in the composites are investigated to optimize the ME output. It is revealed that ME resonances are caused by electromechanical resonance in the piezoelectric phase and magnetomechanical resonance in the magnetostrictive phase. Maximum magnetoelectric voltage coefficient resonance values of 6.7 V/cm Oe at 132.6 kHz and 6.12 V/cm Oe at 427.2 kHz for the composite with optimized PZT volume fraction of 0.55 were obtained at optimized magnetic bias of 0.6 kOe. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A magnetoelectric (ME) hybrid structure is constructed by an efficient coupling between magnetostrictive Terfenol-D (Tb[SUB0.27-0.30]Dy[SUB0.73-0.70]Fe[SUB1.90-1.95])/epoxy and piezoelectric lead-zirconate-titanate [(Pb(Zr[SUB0.52]Ti[SUB0.48])O[SUB3]]/epoxy composites. Significant ME effect produced by the piezoelectric k[SUB31] coupling with the longitudinal vibration of the magnetostrictive component over a wide range of frequency is observed. It is revealed that the ME effect can be enhanced by applying an optimized magnetic bias. A magnetoelectric voltage coefficient as high as 8700 mV/cm Oe is recorded at the resonance frequency of 59.2 kHz for the structure with an optimized magnetic bias of 0.7 kOe. Our measurement confirms that the eddy current loss remains negligibly small at an operating frequency as high as ∼200 kHz, predicting very promising applications of the present ME structure. [ABSTRACT FROM AUTHOR]

A ferromagnetic shape memory alloy was utilized to construct a Ni43Mn41Co5Sn11/Pb(Zr,Ti)O3 laminate. Large direct and converse magnetoelectric (ME) effects were observed at resonance frequencies around the martensitic transition temperature of Ni43Mn41Co5Sn11 alloy, and the temperature affects the ME properties remarkably. The ME coefficients respond almost linearly to the applied ac electric or magnetic field. The mechanism of both direct and converse ME effects in the laminate is discussed. [ABSTRACT FROM AUTHOR]

The specific heat of La0.4Ca0.6MnO3 in bulk and nanoparticle (∼60 nm in grain size) forms was investigated. It is found that the charge-ordered state highly stabilized in the bulk samples can be significantly suppressed in the nanoparticle. The low temperature specific heat data reveal a Schottky-like anomaly at ∼5 K for the bulk sample, while a large electronic linear term (γ=17.8 mJ/mole K2) was identified for the nanoparticle samples. The magnetic measurements unveil the small magnetic entropy as low as ∼0.255 J/kg K and the possible existence of a Griffiths-like phase in the nanoparticle samples. We argue that the physics underlying the size effect is associated with the dimension-dependent interactions based on which the ferromagnetic/charge-ordering transition occurs. [ABSTRACT FROM AUTHOR]