Most of you buy and use magnetic jewellery. Well and good. You must also know how magnets used by gem & Jewellery industry fare in terms of magnetic strength. Here are five indicators that tell you the level of magnetic power.
1. Coercive Power: This is a shortened form of ‘coercive magnetic field strength”. Often abbreviated as “ Hc”, it indicates the point where a magnet loses its relative power vis-à-vis another external magnetic source. Alternatively we can say the point where the magnet gets de-magnetized by the presence of another magnet. This indicator is given as Mega Gauss Oersted (MGOe or simply as Oersted). The higher the Oersted the higher the coercive power. Neodymium demonstrates the highest coercive power for all magnets at 12,300 Oersted whereas Alnico has the lowest Oersted of 640.
2. Magnetic Flux Density: Also known as “Residual Magnetic Flux Density” and abbreviated as “Br” this indicates the maximum magnetic field strength that can be produced and sustained by a magnet. It is given in Gauss rating. Higher is better. Neodymium records the highest maximum flux density of 12,800 Gauss while Ceramic Ferrite ticks the lowest at 3,900.
3. Overall Energy Density: Related to the above two indicators, the overall energy density is given as an integer. It is often abbreviated as “Bmax”. Highest overall energy density is shown by the most robust one. Neodymium has the highest overall energy density of 40. Lowest Bmax of 3.5 is associated with Ceramic Ferrite.
4. Operating Temperature: Abbreviated as “Tmax”, this shows the maximum operating temperature up to which the magnet can function without losing its magnetic field. When this point is exceeded the magnet loses its strength and after cooling down it regains the magnetic field. Alnico has the highest Tmax of 540 degree Celsius. Contrarily the all-powerful Neodymium can be operated only up to 150 degree Celsius.
5. Curie Temperature: Abbreviated as “Tcurie” this indicates the temperature point where a magnet becomes permanently disabled and demagnetized. Once again Alnico shows the highest Curie temperature of 860 degree Celsius and once again Neodymium can be permanently disabled at 310 degree Celsius.
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