Spin chemical potential

[amjad-sh]

Can somebody give me some insights related to spin chemical potential ?
I searched on google but didn't get satisfied.
What it means when two spin groups of electrons (group A with spin up and group B with spin down)have different spin chemical potential?

 

[BigJDubs]

Spin chemical potential is a concept in physics that describes the energy cost of adding an extra spin to a system. It is related to the difference between the chemical potentials of the two spin groups, A and B. In other words, it is the difference between the energy needed to add one extra spin-up particle to group A compared to the energy needed to add one extra spin-down particle to group B. When the spin chemical potential for a system is positive, it indicates that it is energetically favorable to add a spin-up particle to group A than it is to add a spin-down particle to group B. Conversely, when the spin chemical potential is negative, it indicates that it is energetically more favorable to add a spin-down particle to group B than to add a spin-up particle to group A. The spin chemical potential can also be used to describe the degree of spin polarization in a system. For example, if the spin chemical potential is positive, it indicates that the system is spin polarized, meaning that there are more spin-up particles than spin-down particles. Conversely, if the spin chemical potential is negative, it indicates that the system is not spin polarized.