  In this work, we study the effects of magnetic fields and rotation on the
structure and composition of proto-neutron stars (PNS's). A hadronic chiral
SU(3) model is applied to cold neutron stars (NS) and proto-neutron stars with
trapped neutrinos and at fixed entropy per baryon. We obtain general
relativistic solutions for neutron and proto-neutron stars endowed with a
poloidal magnetic field by solving Einstein-Maxwell field equations in a
self-consistent way. As the neutrino chemical potential decreases in value over
time, this alters the chemical equilibrium and the composition inside the star,
leading to a change in the structure and in the particle population of these
objects. We find that the magnetic field deforms the star and significantly
alters the number of trapped neutrinos in the stellar interior, together with
strangeness content and temperature in each evolution stage.
