Magnetizing a ferromagnetic material

[abdulbadii]

TL;DR Summary

How do we magnetize a ferromagnetic material the easiest way

How do we magnetize a ferromagnetic material the best, easiest way, e.g., can we just let it sit around strong magnets in a particular position?

 

[cmb]

Just put it into a magnetic field.

Do you mean that it then holds the magnetic field? This is a function of the material and is called its remanence.

The ability of a duly magnetised mass to retain the ("remanent") field is called coercivity.

To fully saturate a permanent magnet, heat it to above its Curie temperature (the point at which it is no longer ferromagnetic) and expose it to a saturating field as it cools down.

 

[abdulbadii]

just found a cylindrical/tube/circular graphite, material for acquired magnet, difficult get magnetized compared to carbon/stainless steel when both sit around strong magnets in the same position

So would it be the coercivity of the latter higher than the former, and must be worked with the last explanation?

 

[cmb]

Graphite will not make a magnet. You are probably looking at a ferrite material.

Ferrites (metal oxides and other materials sintered together) have some significantly different properties to ferromagnetic materials and cover a very wide range of behaviours. It would be impossible to answer your question directly unless you know exactly what the material is, and even then ferrites have very difficult-to-measure-or-predict non-linear properties.

In general ferrites are 'soft' which means they have low remanence (the material's internal field vanishes more easily when the external field is removed), which is a feature you might want in, for example, a high frequency transformer.

But those ferrites that can be magnetised tend to have quite a good coercivity (resistance to demagnetisation) but none have a particularly high saturation flux (i.e. not particularly strong compared to iron cores).

Carbon steels are usually 'hard' and will hold a field after exposure to an external field. The more carbon the harder the steel, in general. Pure iron has very little remanence but can be formed into a magnet by the process above of heating and cooling in a field, and will also develop a field by simply being hammered in a magnetic field, even the Earth's magnetic field.

Stainless steels are only magnetic when they have a Martensitic crystal structure. Austenitic stainless (most of what you might buy from a regular shop) is non magnetic. The phase may change under mechanical modifications, for example if a sheet of Austenitic is pressed and formed into a sink shape, the work-hardening that occurs on the curves may form Martensitic phases, so if you roam around a sink with a magnet you'll find it is slightly magnetic on the curvy bits but not magnetic on the flat bits.

To make a 'regular' magnet from 'regular' metals, use mild steel components, such as mild steel rods or threaded studs and bolts, these are the easiest materials to find on the basis of making the strongest magnet versus ease of finding something suitable. ('Mild' means not too much carbon, but enough for its engineering strength and enough to hold a remanent magnetic field.)