Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

I've known for a long time that if you heat a magnet, there is a point it loses its magnetism (the Curie temperature). It isn't clear to me if this applies to induced magnetism like iron sticking to a magnet.

Will molten iron behave like a ferrofluid and be attracted to a magnet or will it just have a very weak paramagnetic attraction?

share|improve this question

1 Answer 1

up vote 8 down vote accepted

The loss of magnetism at the Curie temperature applies primarily to "induced magnetism like iron sticking to a magnet".

Ferrofluid doesn't really include a molten iron; ferrofluid is a collection of many small but mezoscopic particles, "sawdust", and its magnetism doesn't differ so much from magnetism of normal pieces of iron except that it's easier for the particles to change the orientation. Ferrofluid normally have lots of "normal fluid" in it, like water or organic liquids, and some "coating", so the ferromagnetic material is a relatively minor component and it's surely not melted.

When a ferrofluid gets heated to the Curie temperature, it loses its magnetism, too.

The Curie temperature of all sensible materials is and has to be below the melting point. When you approach the melting point while heating the material, the magnetism has been lost for quite some time.

Yes, molten iron is paramagnetic, much like every ferromagnetic material above the Curie temperature.

share|improve this answer
    
Thank you for answering one of the outstanding questions of my childhood! I will accept shortly. –  Brandon Enright Mar 28 '13 at 6:07
    
Wow, did you melt iron and magnets when you were a kid? ;-) –  Luboš Motl Mar 28 '13 at 6:27
    
If I'd melted iron when I was a kid I would have answered my own question :-p I was absolutely obsessed with magnets and I always thought it would be awesome to see what a liquid would look like sticking to them. Unfortunately liquid iron is hard to test with! –  Brandon Enright Mar 28 '13 at 6:33

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.