Quenching

In a crystal, \(L_z\) may not be a good quantum number (i.e. a good constant of motion). When \(\langle L_z\rangle=0\), then the OAM is quenched. For example, placing \(p_j\) orbitals between two layers of positive ions in the \(xy\) plane changes their energy from the free electron model. However, both \(E[p_x]\) and \(E[p_y]\) are degenerate, but \(E[p_z]\) is split (lowered \(E\)).

If electrons cannot jump from one orbital to another (i.e. what causes OAM), then the OAM is said to be quenched. The electron cannot freely precess along the degenerate \(m_\ell\) states.

It is of high importance in Transition metals, and in the reason why OAM is not usually considered in magnetization unless SOC is present (see joSpintronicsMeetsOrbitronics2024). However, the \(t_{2g}\) transition-orbitals are slightly less quenched.

Materials with OHE do not agree with a OAM-quenching argument.

Quenching is the reason why, unless there is SOC, most materials neglect OAM in the calculations of total angular momentum.

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