Magnetic Neutron Stars in f(R) gravity
  Neutron stars with strong magnetic fields are considered in the framework of f(R) gravity. In order to describe dense matter in magnetic field, the model with baryon octet interacting through $\sigma$$\rho$$\omega$-fields is used. The hyperonization process results in softening the equation of state (EoS) and in decreasing the maximal mass. We investigate the effect of strong magnetic field in models involving quadratic and cubic corrections in the Ricci scalar $R$ to the Hilbert-Einstein action. For large fields, the Mass-Radius relation differs considerably from that of General Relativity only for stars with masses close to the maximal one. Another interesting feature is the possible existence of more compact stable stars with extremely large magnetic fields ($\sim 6\times 10^{18}$ G instead of $\sim 4\times 10^{18}$ G as in General Relativity) in the central regions of the stars. Due to cubic terms, a significant increasing of the maximal mass is possible. 
Artyom V. Astashenok, Salvatore Capozziello, Sergei D. Odintsov
gr-qc astro-ph.HE hep-th