Cobalt ferrite thin films of different thicknesses were pulsed-laser deposited onto a fused quartz substrate held at ambient temperature (RT) by varying deposition time. The samples were ex-situ ...annealed at 750°C in air for 2 hours. All the films were characterized by X-ray diffraction, Raman spectroscopy and energy dispersive X-ray analysis. The spontaneous magnetization, 4
πM
S
, was found to be 6130 G for the 50 nm thick sample, and this is higher than that for the bulk cobalt ferrite of 5300 G, by 16%. The 4
πM
S
was found to decrease with the increase in film thickness and an overall decrease of 32% was observed, when the film thickness increased from 50 nm to 600 nm. In contrast the films of the same thicknesses, when deposited at substrate temperature of 750°C showed an increase of 4
πM
S
with the increase in film thickness. The thickness dependence of 4
πM
S
in these nanocrystalline thin films has been explained in terms of the cation distribution and the grain size, which are sensitive to the substrate temperature during deposition.
Lead based relaxor ferroelectric thin films can become very useful due to their excellent electrical properties, provided the growth difficulties and high cost of fabrication which have stymied their ...applications are overcome. Our work describes a systematic study of establishing a set of process conditions for reproducible depositions of 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) thin films on La0.67Ca0.33MnO3 (LCMO) seeded Pt/TiO2/Glass substrates. Films were grown at ambient temperature using RF- magnetron sputtering. Single phase PMN-PT films could be obtained by ex situ thermal annealing in air for 2 h at temperatures of 550 and 650 °C. Films annealed at temperatures lower than 550 °C and films deposited without the LCMO buffer layer showed presence of pyrochlore phase. Effect of annealing temperature, on the microstructure, dielectric and ferroelectric properties of the PMN-PT films has been investigated. Scanning electron micrographs of single phase PMN-PT films show a bimodal grain size distribution for the thin films annealed at 550 and 650 °C. The films annealed at 650 °C yielded a dielectric constant of 1300 and a remnant polarization (2Pr) of 17 C cm−2.
This paper deals with the critical aspects of sintering of crystallizable glass+ceramic system, which is a critical part of low‐temperature‐cofired ceramics (LTCC) process. Densification studies ...clearly revealed the influence of filler's nature especially at lower glass contents (≤70 vol%) and lower sintering temperatures. In this temperature range, marked improvement in density was observed in the order cordierite>fused silica>mullite>alumina. The decisive role played by wetting of glass on filler has been demonstrated using heating microscopy and wetting studies. However, densification was not influenced by the nature of filler at higher glass contents (>70 vol%) and at higher sintering temperatures. This is because in this range of glass content viscous flow of glass dominates the wetting behavior. This paper brings out the salient features responsible for the sintering behavior of anorthite glass+ceramic LTCC composition.
Single phase nano-crystalline zinc ferrite thin films were deposited by RF-magnetron sputtering on quartz substrate at room temperature (RT) in pure Argon environment and annealed (in air) at ...different temperatures. Temperature dependence of magnetization was studied on these films using both VSM and by observing FMR (in X band). Value of exchange stiffness constant (D) was obtained by fitting Bloch’s law to the low temperature magnetization data. The value of D decreased monotonously with the annealing temperature (TA) of the samples. A film annealed at TA = 523 K, exhibited the highest magnetization value. The FMR line width of the films decreased with increase in measurement temperature. At RT (∼293 K), the lowest value of line width (ΔH) was 15 kA/m and 13 kA/m in parallel and perpendicular configuration respectively for the sample annealed at TA = 623 K.
Soft Magnetic Composites (SMC) were prepared by coating of nanocrystalline Fe3O4 particles, synthesized by co-precipitation method, on atomized iron powder of particle size less than 53μm in size ...using epoxy resin as a binder between iron and Fe3O4. Fe3O4 was chosen, for its high electric resistivity and suitable magnetic properties, to keep the coating layer magnetic and seek improvement to the magnetic properties of SMC. SEM images and XRD patterns were recorded in order to investigate the coatings on the surface of iron powder. A toroid was prepared by cold compaction of coated iron powder at 1050MPa and subsequently cured at 150˚C for 1 hr in argon atmosphere. For comparison of properties, a toroid of uncoated iron powder was also compacted at 1050MPa and annealed at 600˚C for 2 hr in argon atmosphere. The coated iron powder composite has a resistivity of greater than 200μΩm, measured by four probe method. A comparison of Magnetic Hysteresis loops and core losses using B-H Loop tracer in the frequency range 0 to 1500Hz on the coated and uncoated iron powder is reported.
Ferrimagnetic bismuth substituted yttrium iron garnet Bi
x
Y
3
−
x
Fe
5O
12 (BiYIG) films with
x
=
1 and 2 pulsed laser deposited onto (111) Gd
3Ga
5O
12 (GGG) substrates were studied using ...magneto-optical (MO) Kerr spectroscopy in the photon energy range of 1.8–5
eV at both polar and longitudinal magnetizations. The interference at lower photon energies provided the refined film thicknesses ranging between 70 and 200
nm. The films were grown under compressive strain and displayed saturation magnetizations (
μ
0
M
s) lower than that of their bulk counterparts due to the presence of nanograins forming BiYIG layers and/or magnetically dead interface layers. The trends in the MO spectra agree with those deduced from the published permittivity tensor data for BiYIG using a transfer matrix model applied to a film (BiYIG)–substrate (GGG) system. Due to the reduced
μ
0
M
s the predicted amplitudes are typically higher. The agreement was improved using effective medium approach or by incorporating into the model MO passive interface layers. The information on MO activity at longitudinal magnetization in the garnet layers below 100
nm presents interest for MO imaging and magnetophotonic devices. The results suggest that the MO Kerr spectroscopy combined with MO Kerr magnetometry may represent a valuable, cheap and nondestructive tool for the characterization of magnetic garnet films less than 200
nm thick.
Stoichiometric and non stoichiometric magnesium ferrite (MgFe2+δO4, δ=0.0, 0.1) were synthesized by the sol gel combustion method resulting in nanocrystalline powders with size ranging from 10 to ...100nm. These powders were calcined at various temperatures (300–800°C). One part of the calcined powder was quenched in liquid nitrogen and the other part furnace cooled. α-Fe2O3 was observed in all calcined samples by XRD and this was also reflected in the magnetization data. Electrical response of MgFe2.1O4+δ spinel phase to 75ppm ethanol was found to be greater than that for a stoichiometric magnesium ferrite.
Co-ferrite thin films were prepared by pulsed laser deposition technique at room temperature, and magnetization was studied as a function of annealing temperature (
T
A
) and annealing time. One set ...of films was quenched immediately after annealing while the other set was furnace cooled. Spontaneous magnetization value, 4
π
M
S
, of the quenched films was observed to be higher than the furnace cooled films in all the cases. Magnetization increases monotonically up to
T
A
=650°C and then became nearly constant with the increase in
T
A
. Magnetization values even higher than the Co-ferrite bulk value of 5300 G was observed in the quenched films annealed at and above 650°C. In the case of furnace cooled films, magnetization decreased with the increase in annealing time, while it remained nearly constant in quenched films. Coercivity values of the quenched films were always found to be lower than those of the furnace cooled films. The observed magnetic properties in the films were attributed to the cation distribution and the grain sizes.
Co0.3Zn0.7Fe2O4 nanocrystalline thin films were deposited by pulsed laser ablation technique on amorphous quartz substrate. These films were as deposited at different substrate temperatures (TS) ...varying from room temperature (RT) to 750 °C. The RT deposited films were ex situ annealed at annealing temperatures (TA) ranging from 150 °C to 750 °C. The magnetic properties of the films were observed to depend on TA and TS. A spontaneous magnetization (4πMS) value higher than that of the bulk was observed in the as deposited film at TS = 750 °C. This film also showed a higher Curie temperature than bulk. These results were explained based on the grain growth and cation distribution in thin films.
We report successful identification and preparation of a glass composition in the CaO–Al2O3–SiO2 phase diagram with a judicious choice of fluxes that met all dielectric, electrical, and thermal ...property requirements for low‐temperature cofired ceramic (LTCC) applications. The glass composition sintered at 900°C attains good density (2.45 g/cc) and does not precipitate any crystalline phase. However, when this glass powder is sintered at the same temperature in the presence of 30 vol% cordierite, crystallization of the anorthite phase is observed, which improves the properties of the composite for LTCC application.
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