**Abstract**

Although extensive substitution studies exist on LaMnO3 perovskites, simultaneous substitution at the La and Mn sites in the low-doping regime is not as common and provides important insights into the subtle balance of various competing effects acting on the crystal structure and the magnetic properties. This chapter presents a study of the evolution of the crystal structure and magnetic properties by simultaneous substitution of magnetic and non-magnetic ions at the perovskite A and B sites, respectively. It will examine some of the ways in which experiments on the evolution of magnetic properties provide a suitable balance scenario between the competitive effects arising from doping at each site. The work discusses the evolution of the Curie-Weiss behavior and the formation of ferromagnetic (FM) clusters above the Curie temperature, whose structure is also dependent on doping.

**Keywords:** perovskite manganites, electron paramagnetic resonance, magnetic clusters, Jahn-Teller distortion, local magnetism
