The magnetic properties of nickel change when it is heated above its Curie point.
At room temperature nickel is ferromagnetic, and a nickel sphere is attracted to a hanging magnet. When the sphere is heated to above 627 K, it is no longer attracted to the magnet, but after cooling it once again becomes ferromagnetic, and jumps up to the hanging magnet.
In contrast to paramagnetic substances, the unpaired electrons in ferromagnetic substances interact strongly and are aligned with one another in large domains, even in the absence of an applied magnetic field. (See first still.) In the presence of a magnetic field the domains align with one another, (See second still) and the substance is strongly attracted by the field. In permanent magnets, the alignment of the individual domains with one another is retained even in the absence of an applied magnetic field.
Alignment of spins below and above 627 K in the absence of a magnetic field are shown in video image 13.
Alignment of spins below and above 627 K in the presence of a magnetic field are shown in video image 14.
- Design and Demonstration
- George Lisensky Beloit College, Beloit, WI 53511
- Text
- George Lisensky Beloit College, Beloit, WI 53511
- Nancy S. Gettys University of Wisconsin - Madison, Madison, WI 53706
- David Phillips Wabash College, Crawfordsville, IN 47933
- Video
- Jerrold J. Jacobsen University of Wisconsin - Madison, Madison, WI 53706