  We consider relativistic coherent states for a spin-0 charged particle that
satisfy the next additional requirements: (i) the expected values of the
standard coordinate and momentum operators are uniquely related to the real and
imaginary parts of the coherent state parameter; (ii) these states contain only
one charge component. Three cases are considered: free particle, relativistic
rotator, and particle in a constant homogeneous magnetic field. For the
rotational motion of the two latter cases, such a description leads to the
appearance of the so-called nonlinear coherent states.
