Talk:Superparamagnetism

Confusing —Preceding unsigned comment added by 67.58.242.126 (talk) 07:05, 27 October 2008 (UTC)

thermal fluctuations

The phrase "thermal fluctuations" is linked to a page on Temperature, which does not discuss thermal fluctuations. RockMagnetist (talk) 21:12, 26 August 2010 (UTC)

Hmm, the link could point to Boltzmann distribution or statistical mechanics or statistical fluctuations. None is quite perfect. Eventually I think thermal fluctuations deserves its own article, I would write it if I had time... --Steve (talk) 03:36, 27 August 2010 (UTC)

Interesting - I see that fluctuations is listed as a topic in statistical mechanics, but there is no link as yet. RockMagnetist (talk) 15:36, 17 September 2010 (UTC)

I decided to create the thermal fluctuations page. It's very skimpy at the moment, but it's needed.RockMagnetist (talk) 22:27, 17 September 2010 (UTC)

Good job! Now maybe there should be a link from temperature to thermal fluctuations... --Edgar.bonet (talk) 13:53, 18 September 2010 (UTC)

Thanks. Maybe a link should be added, but I'm not sure where exactly. Possibly in zeroth law of thermodynamics. --RockMagnetist (talk) 18:05, 28 September 2010 (UTC)

Not sure either. Maybe in Temperature#Overview, close to the mention of Brownian motion. Oh! You already linked Brownian motion to thermal fluctuations. Good!--Edgar.bonet (talk) 19:54, 30 September 2010 (UTC)

Interesting reference

I just found this interesting “topical review”:

Superparamagnetism, Subhankar Bedanta and Wolfgang Kleemann, J. Phys. D 42, 013001 (2009).

It’s a 28 pages long review article with 171 references and 31 citations. I still did not have time to go through it, but it looks like it may be a good reference for this Wikipedia article.
--Edgar.bonet (talk) 08:11, 20 September 2010 (UTC)

Thanks for pointing out this reference. I'll be interested to see what they say. --RockMagnetist (talk) 18:16, 28 September 2010 (UTC)

Split discussion

I suggest that the material on Neel relaxation be made into a separate article. It is the basis of so many subjects besides superparamagnetism - for example, it can be used to calculate the lower size limit for single-domain particles, and with a magnetic field it is the basis for thermoremanent magnetization. Two other choices for title would be Neel-Arrhenius relaxation or Neel-Brown relaxation, but I think the simpler choice is best. --RockMagnetist (talk) 18:30, 28 September 2010 (UTC)

I don't get the lower size limit for single-domain particles. Superparamagnetic particles are single domain. As for the thermoremanent magnetization, it looks to me as being all about the superparamagnetic/blocked transition... --Edgar.bonet (talk) 20:05, 30 September 2010 (UTC)

I often use "single-domain" to mean stable single-domain. The lower limit is then the size at which the blocking temperature is room temperature. As for thermoremanent magnetization, the SP/blocked transition is the starting point (at least for single-domain particles), but a lot of the applications would not belong on a superparamagnetism page. The stuff about time-dependent susceptibility is also, in my opinion, somewhere between stable single-domain and SP. There are many other applications of the Neel theory, magnetic viscosity being one example. --RockMagnetist (talk) 20:14, 30 September 2010 (UTC)

Is blocking temp a property of the material or of the measurement technique

Often 'blocking temp' is used as if it is a property of the material - but in this article it sounds like it is also a property of the measurement technique (depending on the measurement time). Have I misread it ? - Rod57 (talk) 08:36, 12 October 2018 (UTC)

...Single-molecule_magnet#Blocking_temperature says it depends on the measuring technique - Can we say what the measurement time is of the various techniques ? - Rod57 (talk) 08:42, 12 October 2018 (UTC)

@Rod57: You haven't misread it. In the second equation, $\tau _{m}$ is the measurement time. It's inside a logarithm, so the dependence is not strong. However, when paleomagnetists look at thermoremanent magnetization in rocks, the "measurement time" can be many millions of years. It would help to add some examples. RockMagnetist(talk) 15:16, 12 October 2018 (UTC)