MadSci Network: Engineering

Re: Magnetism causing a material to heat up or cool off.

Date: Tue Aug 28 09:22:51 2001
Posted By: Jeff Yap, Materials Engineer
Area of science: Engineering
ID: 998508984.Eg

Hi Milton,
Thanks for writing to us!

The phenomenon you're talking about is called "Induction Heating" 
or "Magnetic Cooling" and it affects any electrically conductive material 
to some extent.  Induction Heating is when you form a coil of wire and run 
an alternating current through it.  If you put any metallic or conductive 
object inside the coil, you'll induce localized "eddy" electrical currents 
in the object.  Since the object has a certain amount of electrical 
resistivity, it will heat up.  If you set the Alternating Current at a low 
frequency, the heat is concentrated in the center of the object.  Higher 
frequencies will heat the surface of the object.

Magnetic Cooling is the flip side of Induction heating.  When you remove 
the part from the magnetic field, it will cool.

Certain materials are more affected thermally by magnetic fields than 
others.  This "magnetocaloric" property determines how much heat is 
generated by how much magnetic field.  Right now, there is research being 
conducted on a Gadolinium/Silicon/Germanium alloy that has the best 
magnetocaloric effect yet discovered.  I think this is the material you 
are referring to.


Magnetic Cooling DOE project
Magnetism FAQ
Ameritherm Inc. 
(Manufacturer of Induction Heating power supplies)
Radyne Corp. (Induction Heater 
Manufacturer)  (You can request literature about the technology from this 

Magnetic Cooler Schematic
Web Elements
If you also search "Inductive Heating" or "Magnetic Cooling" on an 
internet search engine, there are lots of sites with additional info.

I hope this helps!

Jeff Yap
Mad Scientist

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