Timeline for How does applying a critical magnetic field force ferromagnetic order in an anti-ferromagnetic material?
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19 events
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| Jan 17, 2021 at 21:53 | comment | added | Xivi76 | @CGS there are plenty of resources that discuss precession under a magnetic field. depts.washington.edu/jrphys/ph315W08/spinmag.pdf Look at this for example. They rigorously derive that a field pointing parallel to spins doesn't precess the spins. I just wanted to point out the clarification since readers might be confused. | |
| Jan 17, 2021 at 13:45 | comment | added | CGS | Hi @Xivi76 , my apologies, you are correct that what I wrote in my last comment is not what Kittel meant. What I understand Kittel to have meant is exactly what I wrote in the original post. The quote from Kittel above comes at the end of a section where he is writing about the magnetic susceptibility in AFM materials when the magnetic field is parallel to the spin axis. Unfortunately there is no reference. I can't tell you if he has made a mistake, but I doubt it. I can only urge you to get your own copy of Kittel and read the section for yourself. | |
| Jan 16, 2021 at 19:18 | comment | added | Xivi76 | @CGS the last statement in your comment contradicts what's written in the answer. Your last statement in the above comment is what I was indicating. Applying a field parallel to spins doesn't have any effect since the torque will be zero. Applying a perpendicular magnetic field will change the orientation. This is antithetical to what you have written in the main answer : 'Kittel, in Introduction to Solid State Physics, reports that with a strong magnetic field applied in the parallel direction, the spin system will turn from the parallel orientation to the perpendicular orientation' | |
| Jan 16, 2021 at 12:50 | comment | added | CGS | Hi @Xivi76 . The definitions used by Kittel are that parallel means the magnetic field is directed along the axis of the spins and perpendicular means that the magnetic field is directed perpendicular to the axis of the spins. Recall too that in an antiferromagnetic material, if you point the B field along the spin axis, half the spins are pointed in the direction of the field and 1/2 are pointed 180 degrees opposite the field. So, if by pointing a strong field perpendicular to the spin axis ALL spins turn in the direction of the field, that will indeed be a lower energy configuration. | |
| Jan 15, 2021 at 18:55 | comment | added | Xivi76 | Can you post the context? The statement in the comment doesn't indicate direction of magnetic field, just the way how the spin precesses. | |
| Jan 15, 2021 at 18:20 | comment | added | CGS | Hi @Xivi76 . Thanks for your comment. But I rechecked my copy of Kittel and what I have written is consistent with what he wrote (page 482, 5th edition): "In very strong fields the spin system will turn discontinuously from the parallel orientation to the perpendicular orientation where the energy is lower". | |
| Jan 15, 2021 at 8:14 | comment | added | Xivi76 | @CGS I think there is an error in the answer. Applying a magnetic field parallel to spins doesn't impart a torque and hence there is no precession of spins (if you assume zero temperature, no magnons etc). Applying a perpendicular magnetic field will slowly rotate the spins. I think you got these two mixed up. | |
| Dec 31, 2020 at 0:40 | history | bounty ended | livars98 | ||
| Dec 31, 2020 at 0:40 | vote | accept | livars98 | ||
| Dec 29, 2020 at 13:52 | history | edited | CGS | CC BY-SA 4.0 |
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| Dec 29, 2020 at 13:42 | history | edited | CGS | CC BY-SA 4.0 |
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| Dec 29, 2020 at 13:38 | comment | added | CGS | Hi@livars98. I'm glad I re-read the title to your question! It made me look deeper into this subject and discover the concept of metamagnetic transitions, which is I think what you are referring to. I hope this helps! | |
| Dec 29, 2020 at 13:35 | history | edited | CGS | CC BY-SA 4.0 |
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| Dec 29, 2020 at 13:16 | history | edited | CGS | CC BY-SA 4.0 |
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| Dec 29, 2020 at 12:35 | history | edited | CGS | CC BY-SA 4.0 |
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| Dec 29, 2020 at 12:28 | comment | added | CGS | Hi @livars98. I've updated my answer. Hope it helps! If you have more questions, let me know! | |
| Dec 29, 2020 at 12:27 | history | edited | CGS | CC BY-SA 4.0 |
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| Dec 29, 2020 at 4:39 | comment | added | livars98 | Thanks for the answer @CGS. For a person who's fairly new to magnetic theory, would you be able to comment how big 9Tesla actually is? | |
| Dec 29, 2020 at 3:54 | history | answered | CGS | CC BY-SA 4.0 |