Mod-01 Lec-21 Quenching of Orbital Angular Momentum; Ferromagnetism

[@jitendramisra722]

Excellent man of knowledge and kind human being.

[@nabeel123ful]

at the very beginning, he had typos to say 4f electrons protected by 5s and 5p electrons for rare earth element, but I think they should be 6s and 5d electrons.

[@vishnuunni.c9802]

At 10.50,. Its stated that... An imaginary operator acting on a real function gives eigen value equal to zero ?
How ?

[@moglibora]

It's not the eigenvalue, the expectation value would be zero

[@sairamithineni2588]

@@moglibora why would that vanish again

[@shaikwasef6974]

The angular momentum Lz operator acts on a wave function ( say f ) as the following :
-i.hbar.(dow.f/dowphi) = m.hbar.f
if f is a real function, we would not get a real eigenvalue ( m is the magnetic quantum number and is real , hbar is real , hence m.hbar is real ) since the i term on the left cannot vanish.
The only way this equation is satisfied is if the eigenvalue is zero.

[@nabeel123ful]

@@shaikwasef6974 Thanks for your explanation, but why would we force the eigenvalue to vanish instead of questioning the validity of the assumption of a real wavefunction? Of course, this goes back to why would a nondegenerate eigenvector of an operator must be real, which I don't quite get.

[@ishanandwani6113]

T and theta are different ?? at 22:21

[@majjisiva6710]

Theta is nothing but Curie temperature here