  Using the quantum magnetohydrodynamics (QMHD) model, linear dispersion of
magnetosonic waves are studied in a quasineutral quantum electron-ion plasma in
two distinct regimes of nonrelativistic and relativistic degeneracies
considering also the plasma composition effect. It is shown that the
paramagnetic spin effects of the degenerated electrons plays a key role in
dynamics of magnetosonic waves. The linear wave-speed is found to have minimum
value at some degeneracy parameter in such plasmas. This is due to delicate
interplay between relativistic degeneracy and the Pauli spin-magnetization. It
is also revealed that the plasma composition has significant effect on the
linear dispersion in the relativistic degeneracy limit contrary to that of
nonrelativistic case and Zeeman energy has significant effect in
nonrelativistic degeneracy regime unlike that of relativistic one in the linear
perturbation-limit. Current findings can have important applications in both
inertial plasma confinement and astrophysical degenerate plasmas.
