Pyrovus - 31-8-2004 at 00:30
How many ferromagnetic elements are there?
In schools they teach that there is only 3; iron, nickel and cobalt, but apparently gadolinium is also ferromagnetic, and as someone mentioned in
another thread, so is plutonium(!). All the books I have just list the usual well known ones, which makes me wonder just how many little known
ferromagnetic elements there actually are.
[Edited on 31-8-2004 by chemoleo]
chemoleo - 31-8-2004 at 02:43
Or to expand this, how many ferromagnetic compositions are there (i.e. oxides, mixtures of metals)?
I know of Fe3O4, and the niob magnets. Anyone?
vulture - 31-8-2004 at 02:44
Europiumoxide and chromium(IV)oxide.
Esplosivo - 31-8-2004 at 09:43
Interestingly enough certain metal mixtures which possess no ferromagnetic behaviour what-so-ever on their own, become ferromagnetic when they are
alloyed. The only such case I can remeber of is a certain mixture of Manganese, Copper, Aluminium and Antimony, although right now I cannot find the %
composition of such an alloy.
Ferromagnetism, unlike magnetism, depends on the temperature of the respective alloys, oxides or elements. At a temperature higher than a specific
temperature for each of the ferromagnetic substances, known as the Curie point/temperature, the magnetic qualities of such substances vanishes.
It would be also interesting to discuss certain compounds/oxides/alloys with antiferromagnetic properties, such as FeF2, NiO, Cr2O3 and FeCl2 amongst
others.
[Edited on 31-8-2004 by Esplosivo]
neutrino - 31-8-2004 at 10:23
By antimagnetic, do you mean diamagnetic? The most diamagnetic substance is prolytic graphite (only along one axis, though), the most diamagnetic
metal is bismuth. Back to magnets, don't forget samarium-cobaltm, alnico (aluminum-nickel-cobalt), and samarium-ferrite.
Mr. Wizard - 31-8-2004 at 10:34
Oxygen gas and liquid is ferromagnetic. I haven't tried it, but there was a web site demonstrating the attraction of floating oxygen bubbles in a
water bucket being attracted to a strong magnet.
vulture - 31-8-2004 at 11:19
Oxygen is paramagnetic, not ferromagnetic.
Twospoons - 31-8-2004 at 14:12
There's also all the ferrites - a huge range of materials based on iron oxide combined with other metal oxides like Mn, Zn, Ni.
Garnet is another ferromagnetic material commonly used at microwave frequencies.
Alloys of iron, nickel, molybdemum etc give rise to permalloy, supermalloy, mu metal ... the list is endless.
Mr. Wizard - 31-8-2004 at 16:14
Whoops, you are right paramagnet not ferromagnetic for Oxygen. Sometime I see what I want to see.
JohnWW - 2-9-2004 at 11:53
Ferromagnetic metals are found around the middles of the "d" transition-metal series , and the "f" rare-earth series, of the
periodic table, where the numbers of unpaired d and f electrons are greatest. Electrons are added to the d and f orbitals in pairs, with (in the
ground state of the metal, but not necessarily in compounds with strong ligands) each orbital having one unpaired electron before the next half of the
electrons are added.
This is why Fe, with 5 unpaired d electrons in 5 3d orbitals, is the most strongly ferromagnetic metal of the first transition series (Co and Ni being
less so); and why Gd, with 7 unpaired f electrons in 7 4f electrons plus one 6d electron, is likely to be the most strongly ferromagnetic rare-earth
metal. Similarly in the actinide series, in which curium would probably be the most strongly ferromagnetic if it could be prepared as the metal in
spite of its strong radioactivity. (U, Np, Pu, Am are increasingly ferromagnetic).
Ferromagnetism requires the unpaired electrons (as in paramagnetic substances) to be capable of being aligned with parallel spins in the same
direction. By comparison, the elements just before Fe in the periodic table, viz. V, Cr, Mn, are antiferromagnetic, meaning that their d electrons
align with parallel but opposite spins, and no bulk magnetism is observable.
In the case of the ferromagnetic Cu-Mn alloy noted above, of which I was previous aware, neither of the component metals themselves being
ferromagnetic - I have a sample of it, in the form of an apparently "brass" table light holder that is noticeably magnetic. In the case of
this alloy, the d electrons in the conduction band distribute themselves over the atoms of the two metals, approximating to the d electron arrangement
of Co. Cu-Fe alloys are likely to be also ferromagnetic, but less so.
Compounds of such metals, like ferrites, magnetite, CrO2, etc. can be ferromagnetic only in the metals' lower valences, with a sufficient number
of unused unpaired d or f electrons capable of becoming parallel-aligned. Such compounds are often also electrically conducting, due to some d (or
less commonly f) electrons lying in the conduction band.
John W.
unionised - 4-9-2004 at 05:31
Esplosivo,
They are called Heusler alloys.
Happy googling