# Ferromagnetic Materials

| 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.

With frame

4.4.1 Applications and Magnetic Materials

4.1.3 Classifications of Interactions

© H. Föll (Electronic Materials - Script)