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Superparamagnetic Iron Oxide Nanoparticles for Magnetic Hyperthermia Applications
Published in Bhupinder Singh, Rodney J. Y. Ho, Jagat R. Kanwar, NanoBioMaterials, 2018
Yogita Patil-Sen, Vikesh Chhabria
In ferromagnetic materials, all the individual magnetic moments are aligned with each other, and a permanent magnetic field is created in the material. On the other hand, in antiferromagnetic materials, the individual magnetic moments have same magnitude but opposite direction, and hence in such materials the net magnetic moment is zero. In ferrimagnetic materials, although most of the magnetic moments are aligned, some are anti-aligned and hence such materials possess a permanent magnetic field but of less magnitude compared to ferromagnetic materials. Ferri and ferromagnetic materials both can be considered as multi-domains of magnetic moments and when an external magnetic field is applied to these materials, the magnetic moments tend to align themselves in the same direction as that of the applied field. As soon as the magnetic moment in each domain aligns in the direction of the magnetic field, saturation magnetization (Ms) is reached. When the magnetic field is removed, magnetization does not go back to zero and the material possesses magnetic field called remanent magnetization (Mr). A magnetic field of a precise intensity is required in order to bring the magnetization to zero and this field is called coercive field or coercivity (Hc). The magnetization curve of magnetic materials is represented by hysteresis loop as shown in Figure 13.3.
Oxide Nanoparticles in Heterogeneous Catalysis
Published in Varun Rawat, Anirban Das, Chandra Mohan Srivastava, Heterogeneous Catalysis in Organic Transformations, 2022
Garima Sachdeva, Jyoti Dhariwal, Monika Vats, Varun Rawat, Manish Srivastava, Anamika Srivastava
Ferrites are chemical compounds in powder form possessing ferrimagnetic properties, made from iron oxides as their fundamental component. They can be categorized into hexagonal (MFe12O19), garnet (M3Fe5O12), and spinel (MFe2O4) form, where M stands for one or more divalent transition metals (Zn, Mn, Co, Ni, Cu). Transition metal ferrites are used in catalysis, as they can be easily recovered with the help of a magnet after the reaction completion. Various types of transition metal ferrites, along with their applications, are described below.
A Conceptual Introduction to the Fundamentals of Magnetic Fields, Magnetic Materials, and Magnetic Particles for Biomedical Applications
Published in Jeffrey N. Anker, O. Thompson Mefford, Biomedical Applications of Magnetic Particles, 2020
There is also a class of materials that exhibit antiferromagnetic exchange interactions but with different magnitude atomic magnetic moments on each antiparallel sublattice (Figure 2.19b). The imbalance of magnetic moments on the two sublattices results in a net magnetization for the material. As such, ferrimagnets behave much like ferromagnets. Examples of ferrimagnets include the iron oxides magnetite (Fe3O4) and maghemite (γ-Fe2O3).
The effect of dysprosium on nickel–cadmium spinel ferrites
Published in Phase Transitions, 2021
Hemant Kumar Dubey, Preeti Lahiri
Ferrites are ceramic ferrimagnetic oxides which are classified into many types that depend on their crystal structures namely spinel, garnet and hexagonal ferrites. Spinel ferrites belong to a class of magnetic materials with general formula AB2O4 where A represents a divalent metal ion while B represents a trivalent metal (Fe) ion. Nowadays, spinel ferrite nanoparticle materials have received attention extensively in materials science and technology due to its many applications in various areas including biomedicine, pharmaceuticals, magnetic resonance image, drug delivery, power transformer electronic circuits, high-frequency devices and so on. Among various spinel ferrites, nickel ferrite, a typical inverse spinel ferrite is a soft magnetic material. The cadmium substituted nickel ferrites are the magnetic materials characterized by maximum permeability, minimum hysteresis losses and low core losses at high frequencies [1] depending on their microstructure (density, porosity, size, shape) as well as macrostructure (crystal structure and elemental composition). Several works are found in the literature on Cd substituted nickel ferrites. The structural and magnetic properties of nanosized Ni–Cd ferrite synthesized by the wet chemical co-precipitation method have been reported [2]. Nikumbh et al. have studied the structural, electrical and magnetic properties as well as cation distribution of cadmium substituted nickel ferrite [3].
In situ neutron diffraction study of the reduction of New Zealand ironsands in dilute hydrogen mixtures
Published in Mineral Processing and Extractive Metallurgy, 2019
Raymond James Longbottom, Bridget Ingham, Mark Henry Reid, Andrew J. Studer, Christopher W. Bumby, Brian Joseph Monaghan
From Figure 2 we can see that for titanomagnetite the magnetic transition was complete by 500°C, evidenced by the relative intensity of the peaks showing magnetic ordering, such as 111 and 331, which decrease to their high-temperature values. According to literature, the Curie temperature Tc of pure magnetite (ferrimagnetic to paramagnetic transition) is around 565–583°C (Néel 1955; Levy et al. 2012). However, the Tc of titanomagnetite is expected to decrease systematically with titanium content (Lattard et al. 2006), with a Curie temperature of 500°C corresponding to Ti substitution of around 6–7 wt-%.
Magnetically separable nanocomposites based on ZnO and their applications in photocatalytic processes: A review
Published in Critical Reviews in Environmental Science and Technology, 2018
Maryam Shekofteh-Gohari, Aziz Habibi-Yangjeh, Masoud Abitorabi, Afsar Rouhi
One of the most important ferrimagnetic materials is certain double oxides of iron and other metals, named ferrites. However, all oxide ferrites do not have ferrimagnetic properties (Phuruangrat, Maisang, Phonkhokkong, Thongtem, & Thongtem, 2017). The magnetic ferrites with different crystal structures are divided into two groups: 1) cubic and 2) hexagonal structures. Cubic structure has the general formula of MFe2O4, where M is a two valent cations of metallic elements such as Mn, Ni, Fe, Co, and Mg. These ferrites have the spinal structure and are sometimes called ferrospinels, due to their crystal structure which is closely related to mineral spinel (MgO.Al2O3). In cubic structures, the large oxygen ions are gathered in a face-centered phase and much smaller metal ions are settled within the spaces. For these structural configurations, there are two kinds of spaces. One is known as tetrahedral or A site, which is located at the center of a tetrahedron with oxygen ions at the corners. The other one is octahedral or B site, which is located at the corners of an octahedron with oxygen ions around it. Hexagonal structures have the general formula of MO.6Fe2O3, where M is bivalent metal ions such as Ba and Sr, which are magnetically hard. Magnetic materials with high coercivity are called hard and are not easily demagnetized (Liu, 2012). CoFe2O4 is magnetically hard, but all of the others are magnetically soft (Cullity & Grahamam, 2011). Exchange coupling between hard magnetic and soft magnetic phases (low coercivity) increases the coercivity and remanent magnetization, which successfully used in multi-phase permanent magnets (Kolhatkar, Jamison, Litvinov, Willson, & Lee, 2013). Soft magnetic materials are easy to be recycled and have attracted the attention of scientific community as potential materials for magnetic separation application in photocatalytic processes (Jia et al., 2017).