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Thermodynamics
Published in Harshad K. D. H. Bhadeshia, Theory of Transformations in Steels, 2021
Diamagnetism is a weak, temperature independent negative susceptibility which causes the material to be repelled by a magnetic field. Any substance whatsoever can be diamagnetic. As discovered by Landau, an electron gas such as that associated with metallic bonding will exhibit diamagnetism because in a magnetic field, the electrons move within the metal in spirals, but in a quantised manner, about the field direction. This induced current results in a magnetic moment which, according to Lenz's law, opposes the applied field. Lenz's law states that when the flux through an electrical circuit is changed, an induced current is set up in a direction that opposes the change in flux. The real scenario may be more complex in a metal because the electron gas moves under the influence of the periodic potential associated with the ion cores within the crystal structure.
Magnetic Behavior of Nanostructured Materials
Published in Sam Zhang, Dongliang Zhao, Advances in Magnetic Materials, 2017
M. R. Hossain, Animesh Kumar Basak, Alokesh Pramanik, Al Mahmudur Rahman
Diamagnetic means repelled by both poles. Diamagnetism appears in all materials and is the tendency of a material to oppose an applied magnetic field and therefore, to be repelled by a magnetic field [80]. Despite its universal occurrence, diamagnetic behavior is observed only in a purely diamagnetic material. In a diamagnetic material, there are no unpaired electrons, so the intrinsic electron magnetic moments cannot produce any bulk effect. In these cases, the magnetization arises from the electrons’ orbital motions. Compared to paramagnetic and ferromagnetic materials, diamagnetic materials, such as carbon, copper, water, and plastic, are even more weakly repelled by a magnet. The permeability of diamagnetic materials is less than the permeability of a vacuum. All substances not possessing one of the other types of magnetism are diamagnetic. Although force on a diamagnetic object from an ordinary magnet is far too weak to be felt, using extremely strong superconducting magnets, diamagnetic objects such as pieces of lead and even mice can be levitated, so they float in midair. Superconductors repel magnetic fields from their interior and are strongly diamagnetic. A schematic representation of diamagnetism in the presence and absence of an external magnetic field is shown in Figure 1.16.
Solid Mixtures
Published in Enrique Ortega-Rivas, Unit Operations of Particulate Solids, 2016
A particle of a given material exposed to a magnetic field will become magnetized to some extent and may act as a magnetic dipole. When plotting the intensity of the applied magnetic field H and the magnetization induced in the particle M, the resulting graphs represent the three ways in which magnetized materials may behave (Kolm, 1975). The materials thus classified, as illustrated in Figure 9.9, are: ferromagnetic, paramagnetic (magnetically attracted), and diamagnetic. The relationship M/H is known as the susceptibility. Paramagnetic substances have positive susceptibilities, and induced magnetization increases the magnetic-flux density within the substance. Diamagnetic materials have negative susceptibilities, and an induced field in this case cancels part of the magnetic-field intensity. Permeability µ, which is often used somewhat imprecisely in referring to ferromagnetic substances, is the ratio of the magnetic-flux density to the magnetic-field density. Magnetization of different materials is dependent directly on the degree of magnetic susceptibility and the applied magnetic field intensity. As can be seen in Figure 9.9, ferromagnetic materials quickly become magnetically saturated so that an increase in the intensity of the magnetic field bears no further effect after a certain point. Paramagnetic materials, on the other hand, follow a direct proportion for the magnetic-flux density and the magnetic-field intensity. Some of these substances cannot be, virtually, saturated.
Tridimensional electric field effect on diamagnetic susceptibility and polarisability of a donor impurity in a double quantum dot
Published in Philosophical Magazine, 2023
Reda Arraoui, Ed-Dahmouny Ayoub, Ahmed Sali, Kamal El-Bakkari, Mohammed Jaouane, Abdelghani Fakkahi
By definition, the susceptibility of a sample is an extensive quantity that characterises its reaction to an applied field. The degree of polarisation of a material in regards toward to an applied electric field is measured as electric susceptibility. When we have a response to a magnetic field in the opposite sense of the applied field, we call it diamagnetic. In this respect, the diamagnetic susceptibility is used to investigate the magnetic behaviour of nanostructures. More recently, E. Iqraoun et al. [23] have studied the influence of an electric field applied on the binding energy, the diamagnetic susceptibility and polarisability of a shallow donor in a quantum dot with conical form. One of their results indicated that the field F enhances slightly the , whereas it diminishes when the electronic quantum confinement is strong. To the best of our knowledge, no theoretical research has been conducted on the influence of a tridimensional field F on the diamagnetic susceptibility and the polarisability of a shallow donor impurity in a symmetrical double QD.