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Low Temperatures Changing Magnetic Properties
Name: Jim
Status: educator
Grade: 9-12
Location: IL
Country: USA
Date: N/A
Question:
What materials can be magnetized as temperature is
reduced low enough? For example, is it possible to magnetize zinc
at a low enough temperature?
Replies:
Hi Jim,
To answer your specific question, zinc cannot be magnetized
at any temperature. The term "Curie Temperature" is the
temperature above which a magnetic material looses its
magnetic properties, or conversely, below which it has
magnetic properties. There are no common metals that have a
curie temperature below about room temperature, and only one
(Gadolinium) whose curie temperature is that low; it becomes
magnetic below 293°K (20°C), that is, at room temperature and
below. All other metals and alloys that exhibit magnetic
properties have curie temperatures much higher, usually at
least a few hundred degrees Celsius. There are no metals or
alloys that have Curie temperatures (that is, that can me
made magnetic) by cooling them below room temperature. In
fact, other than Gadolinium, the only metals exhibiting any
magnetic properties are a few members of the 4th period of
the periodic table, for example, Iron or Nickel.
Regards,
Bob Wilson
Materials that are magnetic require lined up unpaired electrons in
one form or another. Some materials (called ferromagnets) have
electrons unpaired at room temperature. Other materials (called
paramagnets) have electrons that are randomly organized, say at room
temperature, but that become organized if the temperature is reduced
so that the atoms are not bounced around too much. Other materials,
like zinc, do not have any electrons that can become unpaired, so
they do not become magnetic at any temperature. These are called
diamagnetic. Sometimes these transitions between paired and unpaired
orientations of electrons are reversible, but in other cases they
are not. So for example some forms of magnetic iron lose their
magnetism if they are heated and cooled.
Vince Calder
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Update: June 2012
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