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In classical electromagnetism, magnetization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material. Accordingly, physicists and engineers usually define magnetization as the quantity of magnetic moment per unit volume. [1] It is represented by a pseudovector M.
A good bar magnet may have a magnetic moment of magnitude 0.1 A·m 2 and a volume of 1 cm 3, or 1×10 −6 m 3, and therefore an average magnetization magnitude is 100,000 A/m. Iron can have a magnetization of around a million amperes per meter.
A neodymium magnet (also known as NdFeB, NIB or Neo magnet) is a permanent magnet made from an alloy of neodymium, iron, and boron to form the Nd 2 Fe 14 B tetragonal crystalline structure. [1] They are the most widely used type of rare-earth magnet .
The coolest of these, 2MASS J10475385+2124234 with a temperature of 800-900 K, retains a magnetic field stronger than 1.7 kG, making it some 3000 times stronger than the Earth's magnetic field. [18] Radio observations also suggest that their magnetic fields periodically change their orientation, similar to the Sun during the solar cycle. [19]
When the temperature rises beyond a certain point, called the Curie temperature, there is a second-order phase transition and the system can no longer maintain a spontaneous magnetization, so its ability to be magnetized or attracted to a magnet disappears, although it still responds paramagnetically to an external field.
Magnetism is the class of physical attributes that occur through a magnetic field, which allows objects to attract or repel each other.Because both electric currents and magnetic moments of elementary particles give rise to a magnetic field, magnetism is one of two aspects of electromagnetism.
A dynamo can amplify a magnetic field, but it needs a "seed" field to get it started. [59] For the Earth, this could have been an external magnetic field. Early in its history the Sun went through a T-Tauri phase in which the solar wind would have had a magnetic field orders of magnitude larger than the present solar wind. [60]
This material has critical temperature of 10 K and can superconduct at up to about 15 T. More expensive magnets can be made of niobium–tin (Nb 3 Sn). These have a T c of 18 K. When operating at 4.2 K they are able to withstand a much higher magnetic field intensity, up to 25 T to 30 T. Unfortunately, it is far more difficult to make the ...