Diamagnetic Levitation
Diamagnetic levitation is a phenomenon in which a diamagnetic material, when placed in a magnetic field, is repelled by the field and levitates. This occurs because the material's atoms create induced magnetic fields that oppose the applied magnetic field, resulting in a repulsive force. Diamagnetic levitation has applications in fields such as materials science, superconductivity, and magnetic levitation technology.
5 Key excerpts on "Diamagnetic Levitation"
eBook - ePubMagnetic Resonance Imaging
Physical Principles and Sequence Design
- Robert W. Brown, Y.-C. Norman Cheng, E. Mark Haacke, Michael R. Thompson, Ramesh Venkatesan(Authors)
- 2014(Publication Date)
- Wiley-Blackwell(Publisher)
...The electron magnetic moments are intrinsic or can be induced and, in this section, the classification of materials according to the different kinds of magnetic dipole moments is laid out. 25.1.1 Paramagnetism The quantum stacking of electrons in an atom or molecule involves a systematic cancelation of spin moments for each pair. An atom with an unpaired electron has a nonvanishing permanent magnetic moment with an associated nonzero dipole magnetic field, and is referred to as ‘paramagnetic.’ While these moments would be randomly distributed in the absence of outside interactions, they would tend to align with an external magnetic field, producing a bulk magnetic moment and a corresponding macroscopic magnetic field augmenting the external field. What arises in a paramagnetic material is an atomic magnetization analogous to the nuclear spin magnetization discussed so often in this book. Because the atomic moment is so much larger than the nuclear moment (Ch. 2), the local field inside (and outside, for that matter) can deviate substantially from the applied field value obtained in the absence of material. Much as it does for the proton spins, thermal motion would also reduce the tendency of the atomic moments to line up along an external field. 25.1.2 Diamagnetism Whether or not there are any permanent magnetic dipole moments, all materials will have induced dipole moments in the presence of time-dependent external (or internal) magnetic fields. The mechanism is the same as that behind Lenz’s law, or more basically, Faraday’s law. As in the discussion of Ch. 7 concerning the currents induced in detector coils, we can use the analogous picture of induced atomic currents which produce counter magnetic fields, tending to cancel the external field...
eBook - ePubElectromagnetics Explained
A Handbook for Wireless/ RF, EMC, and High-Speed Electronics
- Ron Schmitt(Author)
- 2002(Publication Date)
- Newnes(Publisher)
...The field is then slowly decreased to zero. By the end of the process, the object will have a negligible magnetic field. This technique is known as “degaussing.” Summary of Magnetic Materials In summary, some magnetic materials line up with an external field and some materials line up opposite to the field. This result is similar to the way free electrons line up to oppose a field, whereas controlled currents move and/or rotate to reinforce a field. Table 3.1 summarizes some of the types of magnetic materials. Table 3.1 Magnetic Classification of Materials Material Type Description Nonmagnetic No magnetic reaction. Diamagnetic Induced dipole moment opposes applied field. Repelled by bar magnet. Very weakly magnetic. Paramagnetic Induced dipole moment aligns to applied field. Attracted by bar magnet. Weakly magnetic. Ferromagnetic Induced dipole moment aligns to applied field. Attracted by bar magnet. Very strongly magnetic. Has memory and so can be used to create permanent magnets. High electrical conductivity. Ferrimagnetic Type of ferromagnetic material. Induced dipole moment aligns to applied field. Attracted by bar magnet. Very strongly magnetic. Ferrites Type of ferrimagnetic material. Induced dipole moment aligns to applied field. Attracted by bar magnet. Very strongly magnetic. Low electrical conductivity. Superparamagnetic Material mixture: ferromagnetic. particles suspended in a plastic binder. Induced dipole moment aligns to applied field. Very strongly magnetic. Has memory, which allows for uses in audio, video, and data recording. Data adapted from Krauss and Fleisch, Electromagnetics with Applications, 5th Edition, McGraw-Hill, 1999. Table 3.2 gives the properties of a few magnetic materials. The relative permeability of each material is given. Permeability quantifies how a material responds to magnetic fields in a manner analogous to how permittivity quantifies the material response to an electric field...
eBook - ePubGateway to Condensed Matter Physics and Molecular Biophysics
Concepts and Theoretical Perspectives
- Ranjan Chaudhury(Author)
- 2021(Publication Date)
- Apple Academic Press(Publisher)
...Thus, our simple calculation presented above shows that no magnetization is induced in a classical system even in the presence of an external magnetic field, in thermodynamic equilibrium. The above analysis clearly implies that magnetism of materials, as observed, will have to be essentially a quantum phenomenon. Therefore, we will have to deal explicitly with the quantum mechanical Hamiltonians for describing all types of magnetism. To clarify this point, for example, even though the phenomenon of diamagnetism is a universal one and is based on the property of classical electromagnetic induction, the finite diamagnetic response is only obtainable in a fully quantum mechanical treatment of the material system which is coupled to the electromagnetic field. For the other forms of magnetism, however, the microscopic origin itself is quantum mechanical besides the necessity of using quantum variables in the Hamiltonian. The phenomenon of diamagnetism or more precisely, orbital diamagnetism is a universal one, as stated before. Every system in this universe exhibits diamagnetic response, i.e., negative magnetic susceptibility. Its magnitude, i.e., the absolute magnitude of the diamagnetic susceptibility, however, is generally quite small and is very often masked by the higher magnitude of the spin response (positive magnetic susceptibility) from the other forms of magnetism like paramagnetism. The only exceptions are superconductors and some of the band insulators. These above-mentioned systems behave as “super-diamagnets,” where the diamagnetic susceptibility attains the highest value possible v i z. − 1 4 π.. Moreover, these systems have vanishingly small spin susceptibilities. As a result, the overall magnetic response of these systems is very prominently diamagnetic. The origin of orbital diamagnetism is electromagnetic induction, as has been pointed out before...
eBook - ePubRad Tech's Guide to MRI
Basic Physics, Instrumentation, and Quality Control
- William H. Faulkner, Euclid Seeram(Authors)
- 2020(Publication Date)
- Wiley-Blackwell(Publisher)
...As the time decreases (shortens) – in other words, the more rapid the change in the magnetic field – the more the induced current is increased. Faraday's Law of Induction is the basic principle by which MR signals are induced within the receiver coil. Magnetism Magnetic Properties of Matter All matter has magnetic properties. There are three types of magnetic properties: diamagnetic, paramagnetic, and ferromagnetic. Diamagnetic substances have paired electrons in their orbital shells. Diamagnetic substances exhibit a slight negative or repelling effect when placed in an externally applied magnetic field. Diamagnetic substances are said to have a −1 susceptibility. The diamagnetic effect is weak. Gold is an example of a diamagnetic substance. Paramagnetic substances have unpaired electrons in their orbital shells. Paramagnetic substances become magnetized when placed in an externally applied magnetic field. Paramagnetic substances do not retain magnetization when removed from an externally applied field. Paramagnetic substances are said to have a + 1 susceptibility. Gadolinium is an example of a paramagnetic substance. The paramagnetic properties of gadolinium are the reason it is used in contrast agents for magnetic resonance imaging (MRI). Some substances have both diamagnetic and paramagnetic properties...
eBook - ePub- Bill Mantovani(Author)
- 2019(Publication Date)
- In Easy Steps Limited(Publisher)
...Sometimes the magnetic field is quite large and easily detected, but similarly, sometimes it is so small that it is very difficult to detect its existence. Many metals have a magnetic field. The effect is strongest in metals where the atoms are grouped together in a way that produces tiny individual magnets. When these miniature magnets are all correctly aligned, either naturally or through the influence of another magnet or electric current, the material itself becomes a magnet. Iron has excellent magnetic properties. Materials that behave in this way are called ferromagnetic materials. Magnetism and electricity are very strongly linked. Whenever a current flows, a magnetic field is created. This effect can be put to good use – for example, in creating what is called an electromagnet. A coil is wound around a piece of metal that has virtually no magnetic field of its own. When a current is passed through the coil then a magnetic field is created. When the current is switched off, the magnetic field disappears. Very large electromagnets are often seen in use in scrap metal yards, such as for picking up a car body and dropping it into a crusher. Early records show that magnetism was being used as a navigation aid in ancient China. Ferromagnetic material is the term given to a metal whose molecules move freely and so can be easily made to line up and so turn it into a magnet. Magnetic Field All magnets have a magnetic field that surround them and that is strong enough to have an influence on other materials. As the name suggests, a permanent magnet is surrounded by a permanent magnetic field and, as you learned here, is typically a piece of ferromagnetic material. However, not all ferromagnetic materials are permanent magnets. In some, the molecules only temporarily line up when the material is placed in the presence of a strong magnetic field to form a temporary magnet...
