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Satish K. Malik

Bio: Satish K. Malik is an academic researcher from Federal University of Rio Grande do Norte. The author has contributed to research in topics: Magnetization & Antiferromagnetism. The author has an hindex of 15, co-authored 110 publications receiving 1191 citations. Previous affiliations of Satish K. Malik include University of Brasília & Tata Institute of Fundamental Research.


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TL;DR: In this article, a simple precipitation route was developed to synthesize magnetite (Fe3O4) nano-particles with controlled size without any requirement of calcination step at high temperatures.
Abstract: We have developed a simple precipitation route to synthesize magnetite (Fe3O4) nano-particles with controlled size without any requirement of calcination step at high temperatures. The study of these nano-particles indicates an enhancement in saturation magnetization with reduction in size down to ~10 nm beyond which the magnetization reduces. The latter is attributed to surface effects becoming predominant as surface to core volume ratio increases. From the view -point of applications, 10 nm size of magnetite particles seems to be the optimum.

164 citations

Journal ArticleDOI
TL;DR: In this paper, a simple precipitation route was developed to synthesize magnetite (Fe3O4) nanoparticles with controlled size without any requirement of calcination step at high temperatures.

164 citations

Journal ArticleDOI
TL;DR: In this paper, the magnetic and structural properties of stoichiometric and cation-deficient magnetite Fe3−δO4 and γ-Fe2O3 particles were studied using neutron diffraction, magnetic measurements, and Mossbauer spectroscopy.
Abstract: Stoichiometric and cation-deficient magnetite Fe3−δO4 and γ-Fe2O3 particles have been prepared by the chemical method followed by heat treatments The magnetic and structural properties were studied using neutron diffraction, magnetic measurements, and Mossbauer spectroscopy Charge ordering of Fe3+ and Fe2+ and lattice distortion are not observed below the Verwey transition temperature in the stoichiometric and cation-deficient magnetite It is found that the lattice parameter and the Verwey transition temperature decrease as the cation vacancy increases The Verwey transition almost disappears in the Fe3−δO4 sample with δ=0066 Mossbauer spectra show that the ratio of Fe3+/Fe25+ in stoichiometric magnetite can be modified by heat treatment The Fe vacancies on the B sites change the nature of the Verwey transition No cation vacancy ordering is observed for γ-Fe2O3, due to the small amount of cation vacancies in the compound

85 citations

Journal ArticleDOI
TL;DR: The perovskite La1/3Sr2/3FeO3−δ was investigated by neutron diffraction, magnetic and Mossbauer spectroscopy measurements as mentioned in this paper.
Abstract: The perovskite La1/3Sr2/3FeO3−δ was investigated by neutron diffraction, magnetic and Mossbauer spectroscopy measurements. La1/3Sr2/3FeO3−δ undergoes magnetic ordering at T = 190–200 K accompanied by charge disproportionation. Magnetic peaks due to charge ordering are observed below 200 K. The charge ordering is gradually developed below 200 K along with a charge disproportionation, 2Fe4+ Fe3+ + Fe5+. La1/3Sr2/3FeO3−δ shows an antiferromagnetic structure at low temperature. Magnetic moments of about 3 and 1.3 μB were obtained from the neutron diffraction data refinement for Fe3+ and Fe5+ at 15 K, respectively, which suggest that both Fe ions are in a low spin state. These values are significantly lower than those reported by Battle et al for La1/3Sr2/3FeO2.98. Mossbauer spectra indicate that full charge ordering might be reached below 20 K with no Fe4+.

51 citations

Journal ArticleDOI
TL;DR: In this article, the x-ray absorption near-edge structure was analyzed to provide an understanding of the charge state of the constituent Fe ions, and the analysis revealed about 2/3 of Fe cations to be trivalent, increasing to about 3/4 after a 5 h anneal at 450 °C.
Abstract: MnZn–ferrite has been prepared via high-energy ball milling of elemental oxides MnO, ZnO, and α-Fe2O3. Neutron diffraction measurements suggest a high density of vacancies in a spinel structure. The spinel phase appears to comprise 99.8 wt % of the material in the sample milled for 40 h, with the remainder attributable to unreacted α-Fe2O3. The x-ray absorption near-edge structure was analyzed to provide an understanding of the charge state of the constituent Fe ions. This analysis reveals about 2/3 of Fe cations to be trivalent, increasing to about 3/4 after a 5 h anneal at 450 °C. The heat treatment is also observed to induce a cation redistribution in the ball-milled ferrite toward that of a standard processed via ceramics methods. Results from Mossbauer spectroscopy determine the average hyperfine fields in the sample milled 40 h to be 289 and 487 kOe at 295 and 78 K, respectively. The average isomer shift is 0.32 mm/s at 295 K and 0.46 mm/s at 78 K, values which are typical of iron (III) in a spinel ...

48 citations


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TL;DR: Practical Interests of Magnetic NuclearRelaxation for the Characterization of Superparamagnetic Colloid, and Use of Nanoparticles as Contrast Agents forMRI20825.
Abstract: 1. Introduction 20642. Synthesis of Magnetic Nanoparticles 20662.1. Classical Synthesis by Coprecipitation 20662.2. Reactions in Constrained Environments 20682.3. Hydrothermal and High-TemperatureReactions20692.4. Sol-Gel Reactions 20702.5. Polyol Methods 20712.6. Flow Injection Syntheses 20712.7. Electrochemical Methods 20712.8. Aerosol/Vapor Methods 20712.9. Sonolysis 20723. Stabilization of Magnetic Particles 20723.1. Monomeric Stabilizers 20723.1.1. Carboxylates 20733.1.2. Phosphates 20733.2. Inorganic Materials 20733.2.1. Silica 20733.2.2. Gold 20743.3. Polymer Stabilizers 20743.3.1. Dextran 20743.3.2. Polyethylene Glycol (PEG) 20753.3.3. Polyvinyl Alcohol (PVA) 20753.3.4. Alginate 20753.3.5. Chitosan 20753.3.6. Other Polymers 20753.4. Other Strategies for Stabilization 20764. Methods of Vectorization of the Particles 20765. Structural and Physicochemical Characterization 20785.1. Size, Polydispersity, Shape, and SurfaceCharacterization20795.2. Structure of Ferro- or FerrimagneticNanoparticles20805.2.1. Ferro- and Ferrimagnetic Nanoparticles 20805.3. Use of Nanoparticles as Contrast Agents forMRI20825.3.1. High Anisotropy Model 20845.3.2. Small Crystal and Low Anisotropy EnergyLimit20855.3.3. Practical Interests of Magnetic NuclearRelaxation for the Characterization ofSuperparamagnetic Colloid20855.3.4. Relaxation of Agglomerated Systems 20856. Applications 20866.1. MRI: Cellular Labeling, Molecular Imaging(Inflammation, Apoptose, etc.)20866.2.

5,915 citations

01 Sep 1955
TL;DR: In this paper, the authors restrict their attention to the ferrites and a few other closely related materials, which are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present.
Abstract: In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

2,659 citations

Journal ArticleDOI
TL;DR: The magnetocaloric effect and its most straightforward application, magnetic refrigeration, are topics of current interest due to the potential improvement of energy efficiency of cooling and temperature control systems, in combination with other environmental benefits associated to a technology that does not rely on the compression/expansion of harmful gases.

941 citations

Journal ArticleDOI
TL;DR: In this article, a comprehensive survey of the historical development of the science and technology of ferrite materials as well as applications of the ferrites is presented, with a forecast of the future of ferrites in terms of their chemistry.
Abstract: Ferrites—ceramic ferromagnetic materials—have been considered as highly important electronic materials for more than half a century. During this time, the characteristics of commercial ferrite materials, both soft and hard ferrites, have come to approach theoretical values. The quality of commercial ferrites has been improved through accumulated scientific knowledge and advanced technology. This article provides a comprehensive survey of the historical development of the science and technology of ferrite materials as well as applications of the ferrites. The article also offers a forecast of the future of ferrites in terms of their chemistry.

892 citations

Journal ArticleDOI
TL;DR: A survey of the literature for ca. one thousand B-site substituted perovskite oxides can be found in this article, together with their electronic and magnetic properties and properties.

815 citations