Atchaya Sundararajan A ferromagnetic material has a critical temperature called Curie temperature, above this temperature, the material has a paramagnetic behavior. Marie Curie was the first to discover that there is a critical temperature for each ferromagnetic material above which the material behaves as a paramagnetic. When the temperature increases, the thermal movement competes with the ferromagnetic tendency for the dipoles to align. When the temperature rises beyond a certain point, called the Curie temperature, there is a second order phase transition and the system can no longer maintain a spontaneous magnetization, although it still responds paramagnetically to an external field. Below this temperature, there is a spontaneous breaking of symmetry and random domains are formed (in the absence of an external field). Below the Curie point—for example, 770 °C (1,418 °F) for iron—atoms that behave as tiny magnets spontaneously align themselves in certain magnetic materials.

References:

https://www.nhn.ou.edu/~johnson/Education/Juniorlab/Magnetism/2013F-CuriePoint.pdf

https://www.unf.edu/~michael.lufaso/chem4627/ch8_solid_state.pdf

https://unlcms.unl.edu/cas/physics/tsymbal/teaching/SSP-927/Section%2016_Magnetic_Properties_2.pdf

http://www.physics.pub.ro/Referate/FILS_Engleza/BN120_ENGLEZA/III_10_Curie.pdf

Atchaya Sundararajan

I'd be interested in understanding the motivation of your question. Only then can I imagine to be able to give useful remarks. Just now, I would see no reason to make a link between the two notions.

If "thermal stability" is related to stability against breaking chemical bonds, then the mechanism (interactions involved) is very different from what gives rise to magnetic characteristics.

To give you a set of examples: "one class" of magnetic behavior is diamagnetism. However, there are various reasons for a material to be diamagnetic, and they range from thermally very stable (Silicon) to very unstable (Neon, Argon etc.) but also include the noble metals (where the diamagnetic response of the filled valence d-shells is larger than the Pauli paramagnetism of the Fermi sea).

So, from this set of examples alone, you might understand why I would strongly hesitate to make a general statement about any relationship between the phenomenologies of thermal stability and magnetic response.

Dear Kai,

I agree with you that it is difficult to follow the question for giving him a reasonable answer, but it seems to me that your example of diamagnetism is very far of his intention. First of all because diamagnetism doesn't need to involve even a magnetic material: the best diamagnetics are the superconductors.

Perhaps I could try to complement your answers introducing the magnetocaloric effect where the system can decrease its temperature applying an external magnetic field, i.e. allowing to change the thermal energy thanks to change the magnetic order of the material due to the external magnetic field. Another one is to increase the temperature of magnetic nanoparticles thanks to apply one AC external magnetic field. That is the main idea of the magnetic hyperthermia used in medicine.

Hello Daniel,

interesting answer of yours and indeed linking thermal and magnetic properties or processes. I would still not guess that this is where the original question was aiming at. (It would actually be nice if I were wrong!)

I chose the above examples to cover a large range in thermal material stabilities, atomic binding energies ranging from many eV down to the scale of some 10 meV.

Dear Kai,

Yes, I have seen it that you have concentrated in the words "thermal stability" and therefore with the no change at micro-structural level. I think that the person who has done the question is engineer and the atomic structure is not his worry. May be I'm very wrong and in any case I tried only to give a new answer for complementing the fuzzy question.

Have a good sunday!

Kai Fauth , Thank you Sir ..... why I am asking the relation ship between the thermal and magnetic property is i want to relate the thermal stability coresoponding to the magnetic property........ My data for magnetic property is having unique curve..... and i am having diferent thermal property (TGADSC Measurement) thats why iam asking....

Oreci Escobar Da Silva thank you for your answer sir i will refer and ask

Daniel Baldomir thank you sir

Atchaya Sundararajan, I am unable to understand what you write.

What kind of curve are you referring to when you write: " My data for magnetic property is having unique curve" ? What "magnetic property" (which physical quantity) is it, you're addressing there?

Do I understand correctly that you have two (or more) materials where TGA and/or DSC measurements yield differences but magnetic characteristics look (more or less) the same?

I can only guess as long as you don't share specific details on the materials or what quantities exactly have been measured. My guess is that there is no link between the magnetic characteristics and those determined in TGA. However, if there is a magnetic phase transition, it might show up in well-executed DSC. Then, expect any magnetic characteristics to change at this temperature. However, I would regard it as highly unlikely that the temperature of a magnetic phase transition would coincide or correlate with anything you can see in TGA.

I measured vibrating sample magnetometer sir......magnetic moment(y axis ) vs field (G) ..... I suspect there are two types of magentism it exhibits..... I dont know how to tell accurately thats why iam asking the pharse like thermal stability like that

So you measured magnetization curves M(H) at some temperature (several temperatures?). And yes, you're right, the measured quantity is the specimen total moment, and not the magnetization. They are proportional, usually, so the curve looks the same.

Now what feature in the curve(s) makes you think the specimen exhibits two types of magnetism? It might be useful to share the curve(s) in order to assist you.

P.S.: Allow me one remark: if you don't know what your question is, how should others know what to answer? I'm serious here, no insult implied. It seems just utterly difficult to get to the point. If that is a matter of your language skills, consider trying to get some help.

SORRY for the inconvenience sir .....I know how to present the question ....but especially in this question I dont know where to start a question and where to fininsh....thats why this much confusions.......very sorry.......Yes Sir I measured M(H) ......I have two curves....one is having perfect hysteresis like ferromagnets...another is looks like a straight line but that is also having magnetic quantities like coercivity retentivity and all While magnifying the graph that is also having trace of ferro magnet........ It look like superparamagnet but while magnifying the graph I am suspecting ferro magnet

So you have two very different magnetization curves. One of them, you assume, is chracteristic of ferromagnetism. [It could also be a ferrimagnet, you wouldn't probably be able to tell from M(H) alone.] The other one essentialy looks like a straight line (negleting the details for the moment).

Are these curves measured from two different materials?

• If "yes", what's the main difference between the materials? At what temperatures were the two datasets taken?
• If "no", what did yiz di to the sample in between the two magnetic measurements? [any of the thermal analyses?]

P.S.: I have the impression that you hesitate to share your data and/or material details. It really makes the discussion much more difficult! My current guess is still, that there is no conceivable connection between magnetic and thermal properties to be found.

I am not hesistating to share the details about material sir..I felt that I had a less knowledge about my material and I have to learn about it....if my information is wrong there will be negative imperssion on me..so that I am collecting informations about it...and this only the reason for why I didnt mentioned any material.....once I am sure about the nature of the material definitely I will share with all the details .....Thank you sir and sorry If I made any wrong

Yes sir both are same material...both are measured at room temperature...

So, if nominally it's the same material at the same temperature then something's strange.

Many questions, I know. But you have to take a systematic approach...

Thank you sir I will collect informations about it