# Must know about Thulium ferrite magnets

1. Jan 11, 2014

### CosmicKitten

Wikipedia lists, under uses for thulium, that it has potential use for ferrite ceramic magnets. I want to know why, I looked everywhere and I see nothing further on the topic. The link provided by Wikipedia was just to a link to a preview of an ebook called "Extractive Metallurgy of Rare Earths" which just made the same claim without further substantiation.

I want to know, what it is about thulium that would make it attractive to consider in the production of ferrite magnets. Unlike most of the other lanthanides, thulium is capable of forming a +2 as well as a +3 oxidation state, which I figure would make it incorporable into the Me2+ sites in the crystal, as a substitution for say barium or strontium. But what would this do to the magnet? Make it stronger? More heat resistant? Being a lanthanide, it has f-orbitals that can cause it to have funky magnetic properties, is there a computational way to determine these? Would there be any advantages over samarium cobalt or neodymium iron boron magnets that would potentially offset the cost, which I figure is the main reason why there are none of these on the market? Are any of these even currently in research and development?

Sorry, I'm just kind of obsessed with the lanthanides, I want to know all about them, their uses, their properties, particularly their magnetic properties, I consider them the rock stars of the periodic table. I'm studying all the mathematics that I can on my own so that I can understand the tensor equations used to calculate nonlinear optical properties and the quantum mechanics behind bond and lattice energies and wavelengths absorbed and transmitted and I want to know all of it so I can figure out how to calculate the ideal composition and structure and transition temperature of say a superconductor without having to first run through costly trials and errors. Is that an active field of theoretical research?

2. Jan 12, 2014

### M Quack

Thulium ortho-ferrite (TmFeO3) has been reported to be a weak ferromagnet. The other RFeO3 seem to behave in a similar way.

TmNi2B2C is both antiferromagnetic and superconducting at very low temperatures. The other RNi2B2C compounds also have very interesting magnetic and SC properties.

TmRh4B4 also shows coexistence of magnetic order and SC.

The RKKY interaction is very important in determining the magnetic properties of rare earth materials, especially intermetallics. Unfortunately, it depends on the details of the material's band structure. For these kind of materials that is not all that easy to calculate.

http://en.wikipedia.org/wiki/RKKY_interaction

Another important ingredient in RE magnetism are crystal fields. They have a strong influence on the local, single ion anisotropy and sometimes the optical properties. For this it is useful to learn about group theory.

3. Jan 12, 2014

### Staff: Mentor

An example of research - Ferromagnetism and electronic structure of TmB2 (2009)
http://www.cpfs.mpg.de/fplo/pub/PhysRevB_79_104418.pdf

Magnetic Excitations in Thulium Metal (1989)
http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/22/064/22064604.pdf

Magnetoresistance and magnetization study of thulium (1998)
http://www.fys.ku.dk/~jjensen/Book/thulmag.pdf

One would probably want to explore papers in the area of "density field theory" (DFT) and optical or optoelectronic properties of compounds, particularly the lanthanide compounds of interest.

Meanwhile - A LANL webpage mentions "Natural thulium also has possible use in ferrites (ceramic magnetic materials) used in microwave equipment, and can be used for doping fiber lasers. " http://periodic.lanl.gov/69.shtml

JLAB page mentions "Metallic thulium is relatively expensive and has only recently become available. It currently has no commercial applications, . . . ." http://education.jlab.org/itselemental/ele069.html

Applications (by Lenntech)
The pure metal and compound have few commercial uses: because it is very rare and expensive and has little to offer, thulium find little application outside chemical research. Thulium has been used to create lasers. When stable thulium (Tm-169) is bombarded in a nuclear reactor it can later serve as a radiation source in portable X-ray devices. It also has potential use in ceramic magnetic materials called ferrites, which are used in microwave equipment. Thulium-doped calcium sulphate has been used in personal radiation dosimeters because it can register, by its fluorescence, especially low levels.
Ref: http://www.lenntech.com/periodic/elements/tm.htm#ixzz2qCm5sKLg

Chemicool reports "Uses of Thulium" (http://www.chemicool.com/elements/thulium.html): [Broken]

Radioactive isotope 170Tm is produced by bombarding thulium in a nuclear reactor. It has a half-life of 128 days and is used as a portable source of x-rays.

Thulium is used to dope yttrium aluminum garnets (YAG) used in lasers.

Thulium is also used in alloys with other rare earth metals.

Thulium is used in euro banknotes for its blue fluorescence under UV light to defeat counterfeiters.

From - http://avalonraremetals.com/rare_earth_metal/rare_earths/thulium/ [Broken]
Opto-electronics and Electronics: Because of its scarcity and its high cost, thulium does not have many practical applications. It has been used to create laser lights, but production costs have been too high for commercial use. Thulium has been used in high temperature superconductors similarly to yttrium. Thulium potentially has use in ferrites, in a type of ceramic magnet, used in microwave equipment.

Other sites seem to echo some of these uses.

Last edited by a moderator: May 6, 2017
4. Jan 12, 2014

### CosmicKitten

Yes the websites all echo the same basic uses without providing explanations or sources.

So thulium orthoferrite is weak and not worthwhile, at least for use as a strong magnet, how about other ferrite structures?

Is the blue fluorescence due to transitions from electrons in the f-orbitals? There are 13 in the 4f which means that the only transition that could be made would be a change from 1/2 to -1/2 spin, or perhaps a change in magnetic quantum number, but that doesn't involve much of a change in energy, unless the electrons transition into the 5d shell?

Pardon my ignorance of proper electron level terminology, I know a lot of concepts without knowing the proper words for them because studying the words shuts down the mathematical portion of my brain. Mathematically, I can understand the derivation and everything, but I need some problems to do so I can have a working knowledge of how it works.

Can you link to some good problems to do? Math level is not an issue, just clear instructions and perhaps some problems with walkthroughs, minimal instructions because reading too many words makes me unable to figure out the mechanics on my own.

5. Jan 13, 2014

### M Quack

Ashcroft and Mermin's textbook on solid state physics has two very good chapters on magnetism with problems that are worth working through.

BTW, the "Handbook on the Physics and Chemsitry of Rare Earths" started by Gschneidner and Eyring has now 44 volumes of 500+ pages each, so it is a bit difficult to summarize all that in a couple of lines here without skipping some of the more interesting details. (and no, I have not read all 44 volumes).

http://www.elsevier.com/books/book-series/handbook-on-the-physics-and-chemistry-of-rare-earths

But if you want to catch up with all the physics of Thulium compounds, this series would be a good place to start. Not reading the whole thing, obviously, but going through the volume titles and checking the table of contents when the title looks promising. Any good university library should be able to then get you the actual book.

6. Jan 14, 2014

### CosmicKitten

I am amazed that they can get the proper crystal structure just by crushing and sintering the materials together. Can the doping of a material, the exact places that the atoms of a doping material are placed at be precisely controlled?
How does thulium compare to yttrium in making superconductors? Suppose it's calculated that it's ideal for the thulium to be substituted in certain spots that it might not necessarily wind up at? If the superconducting material has a few flaws wouldn't that destroy the superconductivity or lower the transition temperature? Or would that just contribute to 'flux pinning'? For some reason it strikes me as a nanoscale version of wireless energy transfer, where the energy is transferred as magnetic quanta so that there is no energy loss from one atomic 'inductor' to another... Is there a superconductivity theory similar to that?

7. Jan 15, 2014

### PAllen

You can buy some and experiment. It seems to be available now for a good bit less than wikipedia claims. Google:

chemically pure thulium price

and you will find a supplier of 99.99% pure metal at only $3000 per kg. 99.9% pure is only$2200 per kg. A bargain

8. Jan 15, 2014

### CosmicKitten

How about mixed unpurified lanthanide metal, to sort out as an exercise? I should figure out a way of doing it more cheaply... Perhaps have chemistry majors and even high school students do it as class lab projects and then the results can be donated to suppliers so they can sell it for more cheaply.

9. Jan 15, 2014

### M Quack

Or maybe you should talk to the specialists and take a lab tour.

https://www.ameslab.gov/news/inquiry/2010-2-root

Crystal structures and the precise position of atoms is usually determined by powder x-ray diffraction. This work because the grains in the powder are still many many times larger than the unit cell of the crystal. Sintering is not necessary. You can either fill a small capillary with the powder, or mix it up with a bit of silicon grease to fix it on a flat plate sample holder.

10. Jan 15, 2014

### CosmicKitten

Well the X-ray diffraction (something like a CAT scan can be done on these?) would determine the already existing structure, but how does one build the desired structure?

I had an idea to take heating coils that make it into a plasma so that it's ionized and then send the plasma through an array of computer-controlled magnets like a mass spectrometer that measure the change in flux created by the moving charges and adjust their flux depending upon the calculated mass of each of the individual ions so as to curve their trajectory to just the right place. Since there would be an awful LOT of individual atoms to sort out, this would take an awful lot of computing power, or an awful lot of time.

11. Jan 15, 2014

### M Quack

"Building" a desired structure is somewhere between a science and a form of art. There are many different techniques, but they all rely on the crystal structure to be stable under certain thermodynamic conditions (temperature, pressure, etc.).

The simplest method is to just melt all the ingredients, e.g. in an electric arc. This is often called "shake and bake"

Some ionic crystals ("salts") can be grown from solution

If you are lucky you can find a chemical transport reaction
http://en.wikipedia.org/wiki/Chemical_transport_reaction

In flux growth, you use a different metal as a solvent
http://en.wikipedia.org/wiki/Flux_method

The Czochralski method is usually used for very large single crystals, e.g. silicon for the semiconductor industry
http://en.wikipedia.org/wiki/Czochralski_process

http://en.wikipedia.org/wiki/Bridgman–Stockbarger_technique

and so on and so forth. Guessing which method will work under what conditions of temperature etc is the artistic side of crystal growth.