# How is magnetic field created in an atom according to quantum model

How is magnetic field created in an atom according to quantum model? I mean, we are taught about the magnetic field by bohr's model which assumes that electron revolves around the nucleus in a circular path. But in reality it doesn't do so. So the field will keep changing its orientation. And it would be hard to align for them in external magnetic field if they are ferromagnetic or paramagnetic.

Observables like quantised energy levels and quantised angular momentum of an atom are obtained by finding eigensolutions of the Schrödinger Equation (here for the Hydrogen atom).

Separation into three parts allows to obtain the Colatitude and Azimuthal equations which allows to calculate the quantised angular momentum of the hydrogen atom, giving rise to the electron's orbital magnetic moment.

The electron itself also has an intrinsic so-called spin magnetic moment which can only take on two values.

The net magnetic moment of an atom is the vector sum of its orbital and spin magnetic moments.

• so what happens when there is a ferromagnetic material, which is collection of many domains. Now let us in a domain in which magnetic field of all atoms are oriented in such a way that they are in same direction. An atom (say A) is pointing towards a direction then another atom (say ) right next to it should point in just opposite direction by Lenz law. It denies the concept of domain, doesn't it? Commented Nov 7, 2015 at 9:50
• @manshu: what do you mean by domain here?
– Gert
Commented Nov 7, 2015 at 14:38
• @manshu: in a permanently magnetic material a sufficient number of atoms have magnetic moments more or less pointing in the same direction, so these vectors can add up to a net magnetic moment.
– Gert
Commented Nov 7, 2015 at 14:54
• but the two nearby atoms can't give the magnetic moments in the same direction by lenz law.. Commented Nov 7, 2015 at 15:34
• see the pic in the question Commented Nov 7, 2015 at 15:38