Temperature vs Magnetic Strength (Flux) relationship in ferromagnets

[shreyaan]

TL;DR Summary

I've conducted an experiment by placing a magnet onto a hot plate and fixing my magnetometer at a fixed distance from the magnet. Then I turned the hot plate on and logged the change in magnetic strength as temperature rises. Is there an equation which can summarize this relationship?

I've conducted an experiment by placing a magnet onto a hot plate and fixing my magnetometer at a fixed distance from the magnet. Then I turned the hot plate on and logged the change in magnetic strength as temperature rises.
I did some research and found Bloch T3/2 law.

but I'm not so sure about how I can apply it. Will this even work? I'm using temps from 10ºC to 200ºC. I'm guessing M(T) is magnetic strength at temp T (in Kelvins?) and M(0) is magnetic strength at absolute zero. T is current temp and T_C is the curie temperature.

Is there any other equation which can summarize this relationship? If not, is the equation mentioned above right? What do the α and β signify? Are they constants or need to found out empirically.

I'm also unsure whether to use the equation mentioned above or this equation with the power 3/2.

Please feel free to correct me if I've made any mistakes. Thanks for your help!

 

[berkeman]

Welcome to PF.

I'm using temps from 10ºC to 200ºC.

What did you observe for temperatures above about 80C?

And can you show us some plots from the literature for various permanent magnet materials across temperature? (Use the "Attach files" link below the Edit window)

If you could give us some links to the reading you've been doing about this subject,that would be helpful for us as well. Thanks.

 

[Vanadium 50]

To add to @berkeman 's questions - how sure are you that a hot magnetometer reads the same as a cool one?

 

[shreyaan]

Welcome to PF.


What did you observe for temperatures above about 80C?

And can you show us some plots from the literature for various permanent magnet materials across temperature? (Use the "Attach files" link below the Edit window)

If you could give us some links to the reading you've been doing about this subject,that would be helpful for us as well. Thanks.

Hey! This is the graph I got. The temperature is in Kelvins here.

Here are the links I've read so far:
https://en.wikipedia.org/wiki/Spontaneous_magnetization#CITEREFChikazumi1997
https://www.feynmanlectures.caltech.edu/II_36.html#Ch36-S6
plus some research papers...

 

[shreyaan]

To add to @berkeman 's questions - how sure are you that a hot magnetometer reads the same as a cool one?

The magnetometer itself didn't heat up as much. I measures a 2-4ºC increase from start to finish. Plus the magnetometer wasn't right next to the hot plate so that prevented some infrared potentially messing with the electronics. I've attached a diagram of my setup.

 

[shreyaan]

Any help would be appreciated guys!!

 

[berkeman]

There was a similar thread at PF a few years ago, and @Charles Link was able to provide some good help:

I have recently done an experiment testing the effect of temperature on magnetism through measurement of magnetic flux at a constant distance away from the measuring device. I used a range of 0-90 C for neodymium and bar magnets, and found a reasonably linear trend, with a similar slope to what I was expecting from its coefficient of residual induction.

 

[shreyaan]

Thank you, I will have a look.