What is magnetic susceptibility of diamagnetic substance
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Susceptibility is a measure of the extent to which a substance becomes magnetized when it is placed in an external magnetic field. A synonym for susceptibility is "magnetizability".
When matter interacts with the magnetic field, an internal magnetization or polarization (J) is created that either opposes or augments the external field.
If the polarization opposes the applied field, the effective field within the object is reduced, the lines are dispersed, and the effect is known as diamagnetism. If the polarization is in the same direction as the external field, the magnetic lines are concentrated within the object, resulting in paramagnetism, superparamagnetism, or ferromagnetism, depending on the degree of augmentation.
Magnetic susceptibility, is denoted by the Greek letter chi (χ), is defined as the magnitude of the internal polarization (J) divided by the strength of the external field (B):
χ = J / Bo
Since it is the ratio of two magnetic fields, susceptibility is a dimensionless number. Diamagnetic substances have negative susceptibilities (χ < 0); paramagnetic, superparamagnetic, and ferromagnetic substances have positive susceptibilities (χ > 0).
Nearly all biological tissues are weakly diamagnetic. However, some tissues contain focal accumulations of metals such as iron, gadolinium, copper, or manganese that concentrate the magnetic field and are therefore paramagnetic. A few tissues also contain chunky iron-based protein conglomerates (ferritin and hemosiderin) that are superparmagnetic. Other than trace amounts of magnetite that do not contribute to bulk susceptibility, there are no endogenous ferromagnetic substances in the human body. However, many extrinsic metallic foreign bodies and surgical implants are ferromagnetic, and these are commonly encountered in MR imaging.
When matter interacts with the magnetic field, an internal magnetization or polarization (J) is created that either opposes or augments the external field.
If the polarization opposes the applied field, the effective field within the object is reduced, the lines are dispersed, and the effect is known as diamagnetism. If the polarization is in the same direction as the external field, the magnetic lines are concentrated within the object, resulting in paramagnetism, superparamagnetism, or ferromagnetism, depending on the degree of augmentation.
Magnetic susceptibility, is denoted by the Greek letter chi (χ), is defined as the magnitude of the internal polarization (J) divided by the strength of the external field (B):
χ = J / Bo
Since it is the ratio of two magnetic fields, susceptibility is a dimensionless number. Diamagnetic substances have negative susceptibilities (χ < 0); paramagnetic, superparamagnetic, and ferromagnetic substances have positive susceptibilities (χ > 0).
Nearly all biological tissues are weakly diamagnetic. However, some tissues contain focal accumulations of metals such as iron, gadolinium, copper, or manganese that concentrate the magnetic field and are therefore paramagnetic. A few tissues also contain chunky iron-based protein conglomerates (ferritin and hemosiderin) that are superparmagnetic. Other than trace amounts of magnetite that do not contribute to bulk susceptibility, there are no endogenous ferromagnetic substances in the human body. However, many extrinsic metallic foreign bodies and surgical implants are ferromagnetic, and these are commonly encountered in MR imaging.
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Since it is the ratio of two magnetic fields, susceptibility is a dimensionless number. Diamagnetic substances have negative susceptibilities (χ < 0); paramagnetic, superparamagnetic, and ferromagnetic substances have positive susceptibilities (χ > 0). Nearly all biological tissues are weakly diamagnetic.
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