Understanding Spin in Atoms: The Role of Charged and Uncharged Particles"

[jet10]

I have read somewhere that magnetism of material comes from a spinning charge. Protons and neutrons are supposed to have spins too. But neutrons are not charged and yet they produce a magnetic field. Why?

How do you count a spin of let's say an atom anyway? Is the total spin the sum of the spins of the neutrons, protons and electrons? Why is He-3 a fermion and He-4 a boson? Is it just because He-4 has an additional 1/2 spin from its additional proton?

 

[dextercioby]

Spin is an entirely quantum concept.Magnetism,at classical level,is created by moving electric charges,it doesn't matter whether bosons or fermions.Read QM,SM and solid state physics to learn about the quantum explanation of magnetism.
Alpha particle is a boson and has one extra NEUTRON compared to He3.

Daniel.

 

[NateTG]

In on a macroscopic scale, magnetism is associated with moving (not necessarily spinning) charges. There are, for example, magnetic fields associated with straight wires conducting electricity.

'Spin' as the property of an object corresponds to angular momentum, not magnetic moment, so it is possible for non-mangetic objects to have spin. As far as I am aware Neutrons do not interact with a magnetic field in any fashion. However, even in a classical setting, it's not difficult to imagine systems that have zero net angular momentum and charge, but non-zero magnetic moment such as a pair of concentric counterrotating charged rings.

 

[jtbell]

As far as I am aware Neutrons do not interact with a magnetic field in any fashion.

Neutrons do have a magnetic dipole moment: -0.966 x 10^-26 joule/tesla (-1.91 nuclear magnetons). In fact, it's the same order of magnitude as for protons, which have a magnetic dipole moment of +1.41 x 10^-26 joule/tesla (+2.79 nuclear magnetons).

So they must interact with a magnetic field, about as strongly as protons do, as far as their spin is concerned.

 

[selfAdjoint]

The magnetic moment of the neutron led to the conjecture that the neutron was not elementary but composite, long before the quark model came around. In modern terms, the neutron is composed of three quarks, and they are fermions, hence they have spin 1/2. They move around inside the neutron, and so they generate a magnetic moment.

 

[jet10]

Thanks. So the quarks are responsible for the magnetic moment of the neutron.

An alpha particle is a boson, having one additional neutron. What happens when an atom is ionized? Let's say a fermion atom looses an electron or gains an electron. Does it make it a boson? As far as I know, bosons are force carrying particles e.g. photons or phonons and fermions are "matter" particles - correct me if I am wrong. But I would say that an ionized atom is still a "matter" particle.

 

[marlon]

Thanks. So the quarks are responsible for the magnetic moment of the neutron.

An alpha particle is a boson, having one additional neutron. What happens when an atom is ionized? Let's say a fermion atom looses an electron or gains an electron. Does it make it a boson? As far as I know, bosons are force carrying particles e.g. photons or phonons and fermions are "matter" particles - correct me if I am wrong.

correct

But I would say that an ionized atom is still a "matter" particle.

yes, if an initial neutral atom loses and electron is becomes "charged" or more appropriately it becomes ionized. But it is still a matter-particle

regards
marlon

ps : not all bosons are force carries (eg : the Cooperpairs in superconductivity) but all force carriers are bosons

 

[dextercioby]

Thanks. So the quarks are responsible for the magnetic moment of the neutron.

An alpha particle is a boson, having one additional neutron. What happens when an atom is ionized? Let's say a fermion atom looses an electron or gains an electron. Does it make it a boson?

YES.

As far as I know, bosons are force carrying particles e.g. photons or phonons and fermions are "matter" particles - correct me if I am wrong.

You are wrong.Matter fields are either (pseudo)scalar fields or secind class constrained fields...

But I would say that an ionized atom is still a "matter" particle.

Obviously.

Daniel.

 

[jet10]

thanks again.

what happens if I put particles together? e.g. if you put 2 fermion atoms together, does it make it a boson, because the total spin would be a natural number? Does it depend on the no. of particles in it, in order to tell if a solid-state body is a fermion or a boson?

 

[dextercioby]

Let's leave the boson-fermionic character to the microscopic/quantum description.Okay?

Yes,for the first part of the question...

Daniel.

 

[marlon]

thanks again.

what happens if I put particles together? e.g. if you put 2 fermion atoms together, does it make it a boson, because the total spin would be a natural number? Does it depend on the no. of particles in it, in order to tell if a solid-state body is a fermion or a boson?

This is very easy. You can take two fermions and make a boson if and only if the potential energy of the two fermions together is lower as the potential energy of each fermion apart. Given the fact that everything in nature wants to be in lowest possible potential energy-state, this means that the two fermions "prefer to sit together" and therefore form one composed particle that indeed is a boson. This is how two electrons make up a Cooperpair (this is a boson) in the case of superconductivity

marlon

 

[marlon]

You are wrong.Matter fields are either (pseudo)scalar fields or secind class constrained fields...



Obviously.

Daniel.

This is rubbish...i want to challenge you and ask the original poster if this "obvious" "explanation" brought any clarity...Besides dexter , do you even know what you are saying yourself ? Matter-particles are indeed fermions...

this is basic QFT-stuff

marlon

 

[jet10]

no, dexter, i don't understand what want to say. what do you mean by a second class constrained field? or how is the matter field connected with the scalar field?

 

[dextercioby]

Matter field fermions? Think again,Marlon...

Daniel...

 

[dextercioby]

no, dexter, i don't understand what want to say. what do you mean by a second class constrained field? or how is the matter field connected with the scalar field?

Okay...Let's not go into technical details...I could speak an hor without pause about second class constrained fields.
Scalar field is a basic example of matter field.I is the simplest possible matter field,as it doesn't involve constraints..

Daniel.

 

[marlon]

Okay...Let's not go into technical details...I could speak an hor without pause about second class constrained fields.
Scalar field is a basic example of matter field.I is the simplest possible matter field,as it doesn't involve constraints..

Daniel.

Again i restate my challenge. You see i was right: your first explanaition did not help and this won't do either. You don't know what you are talking about because you say nothing here, i am very sorry. Look at any QFT-book, you shall see that fermions are represented by the socalled matterfields. Forces are mediated by gauge-fields. Apparently you don't know this but a matter-particle is an excitation of the matter-field. That is the story, there is no point in trying to argue with this dexter. If you want proof just ask another advisor here or a mentor. Or (and this is my suggestion to you) go study QFT...

marlon

 

[marlon]

not all matter-particles can be represented by scalar-fields. It really depends on what representation you chose. EG : the spinors


marlon

 

[dextercioby]

Marlon,you're so wrong,that i cannot believe you find the strength inside u not to see it...Or u do and you won't accept it,which is even worse...Go study...

Are $\pi^{+}$ and $\pi^{-}$ particles electrically charged...??Are they described by matter fields...?Have u heard of SED?

Daniel.

 

[marlon]

Marlon,you're so wrong,that i cannot believe you find the strength inside u not to see it...Or u do and you won't accept it,which is even worse...Go study...

Are $\pi^{+}$ and $\pi^{-}$ particles electrically charged...??Are they described by matter fields...?Have u heard of SED?

Daniel.

this is irrelevant to this discussion. Point is that fermions are described by matterfields. And YES all matter-particles are described by matterfields.
Do you even know what a matter field is...

really, my friend, WHAT'S IN A NAME ?

marlon

besides, who the hell is talking about electrically charged particles here ?

 

[jet10]

my question is answered, marlon. I will probably deal with QFT later. Matter field and gauge field is something new fo me...

 

[dextercioby]

this is irrelevant to this discussion. Point is that fermions are described by matterfields. And YES all matter-particles are described by matterfields.
Do you even know what a matter field is...

really, my friend, WHAT'S IN A NAME ?

marlon

besides, who the hell is talking about electrically charged particles here ?

Wow,Marlon it took you 4 hours & half to documentate and in the (very) early hours of the morning to come up with a different opinion than the (WRONG) one sustained last evening...

Yes a matter field is any field that isn't gauge field:no constrained (scalar+psuedoscalar) and second class constrained (Dirac,Weyl/neutrino included).

Daniel.

P.S.All these fields are massive...Mybe neutrino in the initial version of SM made an exception...

 

[dextercioby]

Matter-particles are indeed fermions...

That is bull****.That's what i was trying to tell you...Thankfully,u realized...The important thing now is not to forget.

this is basic QFT-stuff

Which u didn't know...

Daniel.

 

[marlon]

That is bull****.That's what i was trying to tell you...Thankfully,u realized...The important thing now is not to forget.



Which u didn't know...

Daniel.

Do you even know what a matter field is?

Ever heard of Grassmann-variables ?

Please, i did my master thesis on this stuff, so i do know what i am talking about. I suggest you go read QFT in a Nutshell or something else, but please stop this sad persuit of yours just because you do not want to admit you know nothing about it. Just like with vaccuumfluctuations and group theory or orbitals and GTR...

marlon

 

[marlon]

my question is answered, marlon. I will probably deal with QFT later. Matter field and gauge field is something new fo me...

no problem, glad to be of help to you. Feel free to ask more questions on QFT and don't mind dexter...you are what you are, right ?!

marlon

 

[dextercioby]

Do you even know what a matter field is?

Ever heard of Grassmann-variables ?

Please, i did my master thesis on this stuff, so i do know what i am talking about. I suggest you go read QFT in a Nutshell or something else, but please stop this sad persuit of yours just because you do not want to admit you know nothing about it. Just like with vaccuumfluctuations and group theory or orbitals and GTR...

marlon

That's not sad,that's TRAGIC...Doing a thesis means DOCUMENTATION...

I worked with Grassmann variables far more than u...

Daniel.

P.S.And u still don't know what matter fields are...

 

[marlon]

That's not sad,that's TRAGIC...Doing a thesis means DOCUMENTATION...

I worked with Grassmann variables far more than u...

Daniel.

P.S.And u still don't know what matter fields are...

Ok, this very mature post clearly proves my point...

sighs, whatever man :zzz:

marlon

 

[somy]

Well, magnetism rise from the moving charge. not the spinning.
Of course in quantum mechanics, we don't have any "spinning" particle. Spin is an intrinsic property of the particle, just like charge and mass.