We report a study of the possible quantum critical point (QCP) in the rare earth substituted colossal magnetoresistive manganite $({\mathrm{La}}_{1-x}{\mathrm{Dy}}_x{)}_{0.7}{\mathrm{Ca}}_{0.3}{\mathrm{MnO}}_3$ with $x=0.347$. A magnetic phase diagram has been proposed in the temperature-field-plane based on the neutron diffraction, small-angle neutron scattering, and ac susceptibility results. We show the role of applied magnetic field to tune the QCP driven by quenched disorder. The implications of the observed QCP phenomenon to understand the physics of the CMR effect and Griffiths singularities in strongly correlated electron systems are discussed.

• Received 31 July 2006

DOI:https://doi.org/10.1103/PhysRevB.74.144427