Observation of a Griffiths phase in paramagnetic La$_{1-x}$Sr$_x$MnO$_3$

We report on the discovery of a new phase boundary above the magnetic ordering temperature in low doped La$_{1-x} $Sr$_x$MnO$_3$ by means of ESR and susceptibility measurements. The observed triangular phase regime in the paramagnetic state is identified as a realization of a Griffiths phase, where disorder in the ferromagnetic bonds leads to the existence of a temperature scale above $T_C$. The influence of quenched disorder to allow for the occurrence of a Griffiths phase becomes evident by its appearance within the Jahn-Teller distorted orthorhombic structure.