What is a magnetically hard material? - Vidyadip

Question

What is a magnetically hard material?

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Answer

A ‘hard’ magnetic material, such as $\text{ALNICO} ($an alloy of aluminium, nickel and cobalt$),$ has high permeability, high retentivity and very high coercivity$-$ of the orders of $1$ tesla and $10^4$ ampere per metre, respectively. In other words, it has a large zero$-$field magnetization, and large reverse field needed to demagnetize. Its hysteresis loop is very broad. Such a material can be made into a permanent magnet, that is, its magnetization will persist indefinitely if it is subsequently exposed only to weak magnetic fields.

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