Search

Yttrium iron oxide (YFeO 3) sample is prepared by sol-gel method. X-ray diffraction (XRD) graph shows highly defined peaks showing that the compound possess crystalline nature. The Rietveld refined XRD data revealed that the sample has orthorhombic structure with P bnm space group. The experimental data of structural parameters is in accordance with DFT calculated theoretical structural parameters.Fourier Transform Infrared Spectroscopy (FTIR) shows that a pure phase of YFeO 3 isbeen formed. Scanning electron micrograph of YFeO 3 reveals that the sample has non uniform grain structure with slight porosity in it. The grains have an average grain size of about 200 nm. Raman spectroscopic studyconfirms the structure and phase purity of the sample. The M-H curve of YFeO 3 shows a hysteresis loop, with a coercive field of 61 Oe and a residual magnetization of 0.516 emu/gm. Weak ferromagnetic nature of YFeO 3 is attributed to the remnant magnetization value, which suggests that Fe+3 spins are slightly canted but not perfectly anti parallel. Room temperature P-E measurement of YFeO 3 shows lossy ferroelectric nature of the sample.Positive Up Negative Down (PUND) measurementsdone on YFeO 3 sample gives the trueswitchable polarization to be0.002 C/cm2.From the ln J versus ln E plot, the slope of the line is found to be 1.25, indicating Ohmic conduction in the sample. At 300 K, 57Fe Mössbauerspectra of YFeO 3 exhibit a single magnetic sextet, confirming the presence of a single Fe site and the absence of any magnetic impurities. The value of Isomer shift is0.37 mm/s, quadrupole splitting is found to be 0.01 mm/s, Line width (Г) = 0.47 mm/s and hyper fine magnetic field (B hf) of 49.8 T are being calculated from 57Fe Mössbauer measurements. [ABSTRACT FROM AUTHOR]

Ho doped TbMnO 3 multiferroic manganites with the formula Tb 1-x Ho x MnO 3 (where x = 0, 0.1 and 0.2) were synthesized through solid state reaction method. Structural characterization has been done using X-ray diffraction and results confirmed single phase nature of the samples. In order to determine the magnetic and ferroelectric transitions in the materials studied, heat capacity measurements have been undertaken at range 2–300 K for 0T, 2T and 5T magnetic fields. From heat capacity studies three transitions were observed in all the samples in the temperature range 10–45 K. These transitions may be due to the ordering of Mn3+ ions and R3+ ions a detailed explanation of which is given below. Magnetocaloric effect has been studied from the heat capacity measurements under applied magnetic field. At 5T magnetic field, the samples exhibited a magnetic entropy change (ΔS) M of ∼1.6 J/mol K and adiabatic temperature change (ΔT) ad of 3–4 K around 10K in the Ho doped TbMnO 3 samples which is considerably high in comparison to earlier reports. Temperature dependences of specific heat (Cp) for Tb 1-x Ho x MnO 3 (x = 0, 0.1, 0.2) manganites at 0T magnetic fields. (b-d) Temperature dependences of specific heat (C P) for Tb 1-x Ho x MnO 3 (x = 0, 0.1, 0.2) manganites at different magnetic fields. Image 1 • Structure, thermal properties of multiferroic Tb 1-x Ho x MnO 3 was studied. • Transition observed at 10K was effected by the magnetic field. • ΔS max and ΔT max values increases as Ho doping increases. [ABSTRACT FROM AUTHOR]

The Gd 5 Si 2 Ge 2 B x (0 < x ≤ 0.125) alloys were investigated to study the influence of Boron addition on the structure, microstructure, magnetic and magnetocaloric properties. Except x = 0.05 alloy, all the other Boron containing alloys under study displayed the presence of major monoclinic Gd 5 Si 2 Ge 2 -type phase along with low volume fraction of hexagonal GdSi-type (5:5 H) secondary phase at room temperature (RT). In the case of alloy with x = 0.05, monoclinic Gd 5 Si 2 Ge 2 -type and orthorhombic Gd 5 (Si,Ge) 4 type mixed phases along with low volume fraction of Gd 5 Si 3 -type (5:3 H) secondary phase were observed at RT. The structural transition (T s ) (orthorhombic to monoclinic) and the Curie transition (T C ) of the monoclinic phase in the x = 0.05 alloy occurred at 293 K and 305 K respectively. These transitions occurred at relatively higher temperatures than those reported in parent Gd 5 Si 2 Ge 2 alloy. At higher concentrations of Boron (x > 0.05), both the transitions, T s and T C shifted to lower temperatures. A maximum magnetic entropy change of 13.6 J/(kg-K) (at 293 K) and refrigerant capacity (RC) of 378 J/kg were obtained in Gd 5 Si 2 Ge 2 B 0.05 alloy which conveys that this alloy has an edge over the parent alloy in terms of operating temperature and refrigeration capacity. [ABSTRACT FROM AUTHOR]

A series of multiferroic materials with the compositional formula Bi 1−x La x Mn 2 O 5 (x=0, 0.1, 0.2 and 0.3) in single phase were prepared by the solid state reaction technique. After characterizing the samples structurally, a systematic investigation of specific heat and magnetization studies were carried out over the temperature range, 2–300 K. Based on these studies, it has been observed that the magnetization versus temperature plots of all the samples are found to split in the ZFC and FC modes and the observed behavior is explained on the basis of magnetic inhomogeneity. Finally, using the specific heat data, the magnetic entropy values were calculated using Einstein model. [ABSTRACT FROM AUTHOR]

Multiferroic materials with the compositional formula, Tb1-xDyxMnO3 (x=0.1, 0.2, 0.3 and 0.4) were prepared by the sol gel technique. After characterizing the samples structurally, a systematic investigation of specific heat has been undertaken, over a temperature range 4-300 K in 0 T and 5 T magnetic fields. All the samples display interesting specific heat behavior exhibiting transitions due to the long range ordering of Mn3+ as well as R3+ magnetic moments. Magnetic field change generates an entropy change of ~1 J/mol K when a magnetic field changes from 0 to 5 T in the vicinity of antiferromagnetic ordering temperature of R3+. The values of adiabatic temperature change is also appreciable to consider these materials as possible magnetic refrigerants at low temperatures. [ABSTRACT FROM AUTHOR]

Abstract: Multiferroic materials with the compositional formula RMnO3 (where R=Gd, Tb and Dy), were prepared by the citrate gel technique. After characterizing the samples structurally, a systematic investigation of specific heat has been undertaken, over a temperature range 4–300K at different magnetic fields. All the samples display interesting specific heat behavior exhibiting transitions due to the long range ordering of Mn3+ and R3+ moments. Magnetic field change generates an entropy change of ~1J/molK when a magnetic field changes from 0 to 5T in the vicinity of antiferromagnetic ordering temperature of R3+. The value of adiabatic temperature change ~3K for a field of 5T is also appreciable to consider these materials as possible magnetic refrigerants at low temperatures. [Copyright &y& Elsevier]

To comprehend the physical, optical and spectroscopic properties of a novel multicomponent glass system with compositional formula 60Li 2 B 4 O 7 -30Bi 2 O 3 -(10-x)Sb 2 O 3 -xMoO 3 (x = 0, 2.5, 5, 7.5 and 10 mol%) has been synthesized by melt quench process. The lack of intense peaks in the XRD confirmed the glassy nature of the prepared samples. On Substitution of Sb 2 O 3 with MoO 3 in lithium tetraborate-bismuthate glasses, a linear decrease in the density and an increase in the molar volume has been noticed. Physical parameters like oxygen packing density, oxygen molar volume and packing density have been computed. Optical energy bandgap evaluated from UV–Visible absorption spectra, declined with increase of MoO 3. Refractive indices exhibited opposite trend with optical energy bandgap and opens applications for non-linear optical devices. Vibrational modes in the as-prepared glasses have been identified by FTIR and Raman spectra. With increase in MoO 3 content, Mo6+ ions transformed to Mo5+ units which in turn converted BO 4 to BO 3 units as confirmed by FTIR and Raman spectroscopies. [ABSTRACT FROM AUTHOR]

Gadolinium-substituted cobalt manganese ferrite nanoparticles with the composition Co 0.6 Mn 0.4 Gd x Fe 2- x O 4 (where x ranges from 0.0 to 0.08, with x = 0.02) were prepared through the sonochemical method. X-ray diffraction reveals that grown samples are single-phase cubic spinel belonging to space group Fd 3 m, where the crystallite sizes decrease with increasing Gd3+ content. At high doping ratios (x > 0.06), there was a slight increase in crystallite size compared to that of pure Co–Mn ferrite (x = 0), while the lattice parameter (a) decreased in the low doping range of Gd (x < 0.06), resulting in a reduction in crystallite size. Bertaut's method confirms that 80 % of the tetrahedral (A) sites were occupied by Mn ions, while the remaining sites were occupied by other cations in the octahedral (B) positions. Gd3+ ions were found exclusively in the octahedral-B sites. Co2+ ions were expected to occupy the octahedral-B site, which was confirmed in this study for the x = 0.0 and 0.02 samples. Field emission scanning electron microscopy shows the samples are agglomerated and have dense structures. Fourier transform infrared and Raman spectra validated the presence of spinel ferrite modes. Dielectric investigations indicate that as the Gd3+ content exceeds x = 0.0, the dielectric constant and dielectric loss decrease at lower frequencies. The observed dielectric behavior exhibited typical dispersion patterns attributed to Maxwell-Wagner polarization. Furthermore, changes in dielectric properties were observed as the Gd3+ content in Co 0.6 Mn 0.4 Gd x Fe 2- x O 4 nanoparticles increased, which can be attributed to the presence of oxygen vacancies and variations in the distribution of Fe3+ ions at both A and B-sites. [ABSTRACT FROM AUTHOR]

Co-Precipitation technique used to synthesize Co x Zn 1-x S ternary compounds. Samples were studied for their ac conductivity between 30 °C and 300 °C, in the range of 50 Hz to 20 MHz. Analysis revealed that AC conductivity of the samples, correlating with the CBH model. It shows a diminishing trend with rise in frequency, and at higher frequencies the value is more or less constant. The dielectric constant increases with an increase in temperature and cobalt concentration, and it reaches a higher value at lower frequencies. When compared, the values of the samples dielectric loss reveal a trend that is consistent with the value of the dielectric constant. The phenomena that was investigated in this research is thought to be caused by cobalt interstitial defects, which are produced when cobalt ions are introduced into zinc sulfide. • AC conductivity of Co x Zn 1-x S compounds exhibit correlated barrier hopping type of conduction. • The grain contribution is more for AC conductivity of Co x Zn 1-x S compounds. • Both є ′ a n d tan δ < ! − − Q 3 : H i g h l i g h t s s h o u l d o n l y c o n s i s t o f 125 c h a r a c t e r s p e r b u l l e t p o i n t , i n c l u d i n g s p a c e s. T h e h i g h l i g h t s p r o v i d e d a r e t o o l o n g ; p l e a s e e d i t t h e m t o m e e t t h e r e q u i r e m e n t. − − > were low in high frequency regime; this behavior indicated that the compound acquires superior optical quality with lesser defects. This is a crucial parameter in designing of optoelectronic devices. [ABSTRACT FROM AUTHOR]