•The magnetization obtained from FMR is found to be 2600 G.•Observation of large negative anisotropy field (HU).•The stress induced in the film is the primary cause for such a large negative HU.•The ...presence of this stress in YIG film was confirmed using multiple GIXRD.•Systematic FMR and dc magnetic studies in the temperature range 4.2 ≤ T ≤ 300 K.
Magnetic properties and FMR of pulsed laser deposited Y3Fe5O12 (YIG) thin film on Gd3Ga5O12 (1 1 1) substrate have been investigated in the temperature range 4.2 ≤ T ≤ 300 K. The effective saturation magnetization (4πMeff), obtained from Ferromagnetic Resonance at room temperature, is found to be 2600 G, which is higher than SQUID measured 4πMS value of 1770 G. This implies that the value of 4πMeff can only be accounted by considering a negative anisotropy field (HU) of around 830 Oe at room temperature. Such an anisotropy is attributed to a compressive stress (−1.70 × 1010 dyne/cm2) induced in the film closer to the film-air interface. The presence of this stress in YIG film was confirmed using multiple {hkl} stress measurements with grazing incidence X-ray diffraction performed at different depth of penetration on the YIG film.
Nano-crystalline magnetic ZnFe 2 O 4 thin films were deposited in oxygen atmosphere at different substrate temperatures (T S ) on amorphous quartz substrate by pulsed laser deposition technique. The ...T S = 350 °C film was also annealed at different temperatures in air. X-ray diffraction patterns confirmed that all the samples were cubic spinel and the average grain size of the films increased with increasing T S and annealing temperatures (T A ). Spontaneous magnetization at different temperature was obtained from the M-H loops. The temperature dependence of magnetization data was fit using Bloch's law. The value of exchange stiffness constant (D) was calculated using the fit values of Bloch's constant. The obtained D values were found to gradually decrease with the increase of average grain size.
BaTiO3 was synthesized by solid state reaction between BaCO3 and TiO2 at 1150°C. XRD analysis of the powder confirmed the formation of phase pure tetragonal powder. The particle size of BaTiO3 powder ...was of the order of 0.7µm. In order to study grain growth kinetics of BaTiO3, isothermal sintering was carried out at 1200, 1250 and 1300°C for the time durations of 2, 4 and 6h at each of these temperatures. Average grain size increased from 0.4µm to 1.1µm on increasing time and temperature of sintering. Corresponding to the temperatures of 1200, 1250 and 1300°C, grain growth exponents obtained using phenomenological kinetic grain growth equation decreased in the order of 9.77, 4.61 and 3.08 indicating rapid coarsening with increased temperature. Grain growth exponents as high as 4.61 and 9.77 can be regarded as the result of mixed diffusion while grain growth exponent of 3.08 can be the result of pore controlled lattice diffusion. Activation energies calculated in correspondence of grain growth exponents of 9.77, 4.61 and 3.08 were 1307±65, 567±30 and 439±20kJ/mol respectively.
Zinc ferrite thin films of varying thickness were deposited at ambient temperature using RF-magnetron sputtering. The films were annealed at temperatures in the range 250 °C to 650 °C in air for 2 ...hrs. The magnetization of the film was observed to depend on the average grain size and also on thickness of the film. It was found that thermal annealing reduces the peak to peak ferromagnetic resonance (FMR) line width. A low in-plane line width of 195 Oe and a line width of 170 Oe in perpendicular configuration was observed for a 240 nm thickness film annealed at TA=450 °C.
Ferromagnetic resonance (FMR) and magnetic studies have been carried out on polycrystalline YIG films deposited by pulsed laser deposition (at T S :750 °C, O 2 :5×10 -2 mbar) using a range of laser ...energies (240 to 350 mJ). The films were ex situ annealed (T a :700 °C, in air for 2 h). The film thickness increases from 100 to 290 nm for an hour of deposition with the increase in laser energy from 240 to 350 mJ. The FMR linewidth was found to reduce from 340 to 70 Oe for the same incremental variation in laser energy. Multiple resonance modes were observed in the perpendicular FMR spectra of our samples which are related to intrinsic as well as extrinsic mechanisms such as in homogeneities. Saturation magnetization measurement (M s ) is found to be dependent on the laser energy. The value of M s is found to increase with laser energy and is close to 90% of the bulk value for the film with highest power. An attempt has been made to correlate the magnetization results with the microstructure.
The observation and theory of a large remanent magnetoelectric (ME) coefficient and coercivity in the static field H dependence of the low-frequency ME effects are reported for bilayers of lead ...zirconate titanate (PZT) and a functionally graded ferromagnetic layer. The grading involves magnetization with the use of nickel zinc ferrite of composition Ni sub(0.7) Zn sub(0.3) Fe sub(2)O sub(4) (NZFO) and pure Ni. In homogeneous bilayers of PZT-Ni or PZT-NZFO, the ME voltage coefficient (MEVC) vs H data do not show any hysteresis or remanence. Upon grading the ferromagnetic layer, significant changes including hysteresis and remanece are observed. In PZT-Ni-NZFO, MEVC vs H data show a positive remnant MEVC and a negative coercive field. When the grading is reversed, in samples of PZT-NZFO-Ni, the remnant MEVC is negative and the coercive field is positive. A theory is proposed for the low-frequency ME effects in the graded composites. According to the model, the grading in the magnetization leads to a built-in magnetic field in the ferromagnetic layer, and this field depends on the sequence of grading and the thickness of the NZFO and Ni layers. As a result, the total torque moment and flexural deformations in the composite and the bias field dependence of ME voltage coefficient becomes strongly hysteretic. Calculated MEVC vs H, remnant MEVC, and coercive field are in good agreement with the data.
•Nanocrystalline zinc ferrite (ZnFe2O4) thin films were investigated.•Magnetoelasticity was studied depending on the samples preparation temperatures.•The annealing is resulted in migration of Fe3+ ...ions from A sites to B site.•Obtained results suggest two-ion character of magnetostriction.
The magnetoelastic properties of nano-crystalline zinc ferrite (ZnFe2O4) thin films prepared by Pulse laser deposition on amorphous fused quartz substrates have been investigated by means of the strain-modulated ferromagnetic resonance, as a function of the substrate temperature during the deposition, and as a function of the annealing temperature. Magnetoelastic constants reveal the same trends as the magnetization, showing correlation between these two parameters. The results are similar to that obtained earlier for the Y3Fe5O12 ferrite.
A study of temperature dependance of magnetization was carried out on nanocrystaline Zn-ferrite thin films deposited using Pulsed Laser Deposition (PLD) at three different substrate temperatures. The ...temperature dependence of the films deposited at ambient temperature, 350 and 850°C showed marked difference in the temperature dependence of their magnetization. While the sample deposited at 850°C showed predominantly antiferromagntic grains, the one deposited at 350°C showed a ferrimagnetic behavior. The ambient temperature deposited film showed mainly superparamagnetic grains.
We have investigated the microstructural and magnetic properties of the post annealed slow cooled and quenched Mg-ferrite thin films. The microstructural properties of these films were studied ...through XRD, TEM and SEM. The magnetic properties were studied using VSM at 300K and 10K. The quenched film showed ∼1.66 times higher magnetization at room temperature (RT) compared to the bulk and the slow cooled film (4πMS of bulk∼1880 Gauss at RT) though the crystal phase, grain size and thickness of both the films were similar. The change in the cation distribution is the plausible origin of large magnetization observed in the quenched (rapid cooled) film.
Yttrium iron garnet (YIG) thin films were deposited on fused quartz substrate at different substrate temperatures (
T
s) varying from room temperature (RT) to 850
°C using pulsed laser deposition ...(PLD) technique. All the films in the as-deposited state were X-ray amorphous and non-magnetic at RT. The film deposited at RT after annealing at temperatures
T
a⩾700
°C showed both X-ray peaks and the magnetic order. The films deposited at higher
T
s (500–850
°C) and then annealed at 700
°C resulted in better-quality films with higher 4
πM
s value. The highest value of magnetization was for the sample deposited at 850
°C and annealed at 700
°C, which is 68% of the bulk 4
πM
s value.
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