Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userGamma irradiated nanostructured NiFe2O4: Effect of gamma-photon on morphological, structural, optical and magnetic properties
71
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The current manuscript highlights the preparation of NiFe2O4 nanoparticles by adopting sol-gel auto combustion route. The prime focus of this study is to investigate the impact of gamma irradiation on the microstructural, morphological, functional, optical and magnetic characteristics. The resulted NiFe2O4 products have been characterized employing numerous instrumental equipments such as FESEM, XRD, UV visible spectroscopy, FTIR and PPMS for a variety of gamma ray doses (0 kGy, 25 kGy and 100 kGy). FESEM micrographs illustrate the aggregation of ferrite nanoparticles in pristine NiFe2O4 product having an average particle size of 168 nm and the surface morphology is altered after exposure to gamma-irradiation. XRD spectra have been analyzed employing Rietveld method and the results of the XRD investigation reveal the desired phases (cubic spinel phases) of NiFe2O4 with observing other transitional phases. Several microstructural parameters such as bond length, bond angle, hopping length etc. have been determined from the analysis of Rietveld method. This study reports that the gamma irradiations demonstrate a great influence on optical bandgap energy and it varies from 1.80 and 1.89 eV evaluated via K M function. FTIR measurement depicts a proof for the persistence of Ni-O and Fe-O stretching vibrations within the respective products and thus indicating the successful development of NiFe2O4. The saturation magnetization (MS) of pristine Ni ferrite product is noticed to be 28.08 emug-1. A considerable increase in MS is observed in case of low gamma-dose (25 kGy) and a decrement nature is disclosed after the result of high dose of gamma irradiation (100kGy).
rate research
Read More
We present a comprehensive structural characterization of ferromagnetic SiC single crystals induced by Ne ion irradiation. The ferromagnetism has been confirmed by electron spin resonance and possible transition metal impurities can be excluded to be the origin of the observed ferromagnetism. Using X-ray diffraction and Rutherford backscattering/channeling spectroscopy, we estimate the damage to the crystallinity of SiC which mutually influences the ferromagnetism in SiC.
Nanocrystalline ribbons of inverse Heusler alloy Mn2Ni1.6Sn0.4 have been synthesised by melt spinning of the arc melted bulk precursor. The single phase ribbons crystallize into a cubic structure and exhibit very fine crystallite size of < 2 nm. Temperature dependent magnetization (M-T) measurements reveal that austenite (A)-martensite (M) phase transition begins at T~248 K and finishes at T~238 K during cooling cycle and these values increase to T~267 K and T~259 K while warming. In cooling cycle, the A-phase shows ferromagnetic (FM) ordering with a Curie temperature T~267 K, while both the FM-antiferromagnetic (AFM) and M-transitions occur at T~242 K. The M-phase undergoes FM transition at T~145 K. These transitions are also confirmed by temperature dependent resistivity measurements. The observed hysteretic behaviour of magnetization and resistivity in the temperature regime spanned by the A-M transition is a manifestation of the first order phase transition. Magnetization and susceptibility data also provide unambiguous evidence in favour of spin glass . The scaling of the glass freezing temperature (Tf) with frequency, extracted from the frequency dependent AC susceptibility measurements, confirms the existence of canonical spin glass at T<145 K. The occurrence of canonical spin glass has been explained in terms of the nanostructuring modified interactions between the FM correlations in the martensitic phase and the coexisting AFM.
In this work we analyse the role of a thin Cr spacer between Fe and Gd layers on structure and magnetic properties of a [Fe(35A)/Cr(tCr)/Gd(50A)/Cr(tCr)]x12 superlattice. Samples without the Cr spacer (tCr=0) and with a thin tCr=4A are investigated using X-ray diffraction, polarized neutron and resonance X-ray magnetic reflectometry, SQUID magnetometery, magneto-optical Kerr effect and ferromagnetic resonance techniques. Magnetic properties are studied experimentally in a wide temperature range 4-300K and analysed theoretically using numerical simulation on the basis of the mean-field model. We show that a reasonable agreement with the experimental data can be obtained considering temperature dependence of the effective field parameter in gadolinium layers. The analysis of the experimental data shows that besides a strong reduction of the antiferromagnetic coupling between Fe and Gd, the introduction of Cr spacers into Fe/Gd superlattice leads to modification of both structural and magnetic characteristics of the ferromagnetic layers.
Nanostructured La0.67Ca0.33MnO3 (NS-LCMO) was formed by pulsed-laser deposition on the surface of porous Al2O3. The resistance peak temperature (Tp) of the NS-LCMO increases with increasing average thickness of the films, while their Curie temperatures (Tc) remain unchanged. The coercive field of the samples increases with decreasing film thickness and its temperature dependence can be well described by Hc(T) = Hc(0)[1-(T/TB)1/2]. A large magnetoresistance and strong memory effect were observed for the NS-LCMO. The results are discussed in terms of the size effect, Coulomb blockade and magnetic tunneling effect. This work also demonstrates a new way to get nanostructured manganites.
Structural and electronic properties of the alpha- and gamma-phases of cerium sesquisulfide, Ce2S3, are examined by first-principles calculations using the GGA+U extension of density functional theory. The strongly correlated f-electrons of Ce are described by a Hubbard-type on-site Coulomb repulsion parameter. A single parameter of $U^/prime$=4 eV yields excellent results for crystal structures, band gaps, and thermodynamic stability for both Ce2S3 allotropes. This approach gives insights in the difference in color of brownish-black alpha-Ce2S3 and dark red gamma-Ce2S3. The calculations predict that both Ce2S3 modifications are insulators with optical gaps of 0.8 eV (alpha-phase) and 1.8 eV (gamma-phase). The optical gaps are determined by direct electronic excitations at k=Gamma from localized and occupied Ce 4f-orbitals into empty Ce 5d-states. The f-states are situated between the valence and conduction bands. The difference of 1 eV between the optical gaps of the two Ce2S3 modifications is explained by different coordinations of the cerium cations by sulfur anions. For both Ce2S3 modifications the calculations yield an effective local magnetic moment of 2.6 $mu_B$ per cerium cation, which is in agreement with measurements. The electronic energy of the alpha-phase is computed to be 6 kJ/mol lower than that of the gamma-phase, which is consistent with the thermodynamic stability of the two allotropes.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
