 |
Here is a list of ferromagnetic (including
ferrimagnetic) materials (from the
"Kittel"). Besides the chemical formula, the
Curie temperature
TC and the
magnetic moment
mm of the molecules (in units of the
Bohr magneton
mB) is listed |
|
|
|
|
|
| Material |
TC [K] |
mm |
| Fe |
1043 |
2.22 |
| Co |
1388 |
1.72 |
| Ni |
627 |
0.606 |
| Gd |
292 |
7.63 |
| Dy |
88 |
10.2 |
| CrO2 |
386 |
2.03 |
| MnAs |
318 |
3.4 |
| MnBi |
630 |
3.52
+ 3.6 Mn
–0.15 Bi |
| EuO |
69 |
6.8 |
NiO / Fe
(Ferrit) |
858 |
2.4 |
| Y3Fe5O12 |
560 |
5.0 |
|
|
|
|
|
The list could be much longer, but we
see a number of interesting facts. |
| |
 |
There exist more elemental ferromagnets than just the common trio
Fe, Ni, Co - but not at room temperature! |
|
|
Elements that do not form a ferromagnetic elemental crystal, may
become from ferromagnetic crystals in combination with some other atoms. This
is especially true for Mn and Cr compounds. |
|
|
There are many "strange"
oxides or mixtures of oxides of non-magnetic elements (EuO) or magnetic
elements that are ferri- or ferromagnetic. Most compounds with the composition
MOFe2O3 and M being some bivalent metal
(including Fe) are ferrimagnets. |
|
|
The total magnetic moment carried by
the atoms or molecules can be rather large; it is a combination of the moments
of the atoms (and, if applicable, whatever free electrons contribute). It is
constructed from positive and negative contributions for ferrimagnets (as shown
for the MnBi case), It is, however not obvious, if the total magnetic
moment from some compound is "ferro" (all contributions same
direction or sign) or "ferri" (different signs). While most oxides
are "ferro", some (e.g. CrBr3, EuO,
EuS) are "ferro". |
|
|
|
|
Here is a list of
anti-ferromagnetic materials;
TC is now the
Néel
temperature |
|
|
|
|
|
| Material |
TC [K] |
| Cr |
308 |
| MnO |
116 |
| MnS |
160 |
| NiO |
525 |
| FeCl2 |
24 |
| FeO |
198 |
| CoCl2 |
25 |
| CoO |
291 |
| NiCl2 |
50 |
| NiO |
525 |
|
|
|
|
|
|
We find the by now usual suspects
Fe, Ni, Co, Mn, Cr and their oxides, but
also plenty of other compounds (mostly not listed). |
|
|
While anti-ferromagnetic ordering
provides endless challenges for solid state physicists, it appears that there
are no practical uses for this magnetic property at present. |
|
|
© H. Föll
7.3.2 Anwendungen außer magnetische Speicher 
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