Ferromagnetic materials Ferromagnetism

the table on right lists selection of ferromagnetic , ferrimagnetic compounds, along temperature above cease exhibit spontaneous magnetization (see curie temperature).

ferromagnetism property not of chemical make-up of material, of crystalline structure , microstructure. there ferromagnetic metal alloys constituents not ferromagnetic, called heusler alloys, named after fritz heusler. conversely there non-magnetic alloys, such types of stainless steel, composed exclusively of ferromagnetic metals.

amorphous (non-crystalline) ferromagnetic metallic alloys can made rapid quenching (cooling) of liquid alloy. these have advantage properties isotropic (not aligned along crystal axis); results in low coercivity, low hysteresis loss, high permeability, , high electrical resistivity. 1 such typical material transition metal-metalloid alloy, made 80% transition metal (usually fe, co, or ni) , metalloid component (b, c, si, p, or al) lowers melting point.

a relatively new class of exceptionally strong ferromagnetic materials rare-earth magnets. contain lanthanide elements known ability carry large magnetic moments in well-localized f-orbitals.

actinide ferromagnets

a number of actinide compounds ferromagnets @ room temperature or exhibit ferromagnetism upon cooling. pup paramagnet cubic symmetry @ room temperature, undergoes structural transition tetragonal state ferromagnetic order when cooled below tc = 125 k. in ferromagnetic state, pup s easy axis in <100> direction.

in npfe2 easy axis <111>. above tc ≈ 500 k npfe2 paramagnetic , cubic. cooling below curie temperature produces rhombohedral distortion wherein rhombohedral angle changes 60° (cubic phase) 60.53°. alternate description of distortion consider length c along unique trigonal axis (after distortion has begun) , distance in plane perpendicular c. in cubic phase reduces c/a = 1.00. below curie temperature

c
a


−
1
=
−
(
120
±
5
)
×

10

−
4




{\displaystyle {\frac {c}{a}}-1=-(120\pm 5)\times 10^{-4}}

which largest strain in actinide compound. npni2 undergoes similar lattice distortion below tc = 32 k, strain of (43 ± 5) × 10. npco2 ferrimagnet below 15 k.

lithium gas

in 2009, team of mit physicists demonstrated lithium gas cooled less 1 kelvin can exhibit ferromagnetism. team cooled fermionic lithium-6 less 150 nk (150 billionths of 1 kelvin) using infrared laser cooling. demonstration first time ferromagnetism has been demonstrated in gas.