Neutron-powder-diffraction study of the magnetic and structural properties of ${\mathrm{Pr}}_{0.6}({\mathrm{Ca}}_{1-x}{\mathrm{Sr}}_x{)}_{0.4}{\mathrm{MnO}}_3$ $(0\mathrm{}<~x<~1)$

We present the results of a neutron-powder-diffraction study in which we have examined the magnetic and structural properties of ${\mathrm{Pr}}_{0.6}({\mathrm{Ca}}_{1-x}{\mathrm{Sr}}_x{)}_{0.4}{\mathrm{MnO}}_3$ $(0\mathrm{}<~x<~1)$ as a function of doping concentration x and temperature. For $x<~0.15$ charge ordering and a Jahn-Teller distortion below 250 K are evident from rapid changes in the lattice parameters and bond lengths as a function of temperature and a transition from a high-temperature orthorhombic to a low-temperature monoclinic structure. For $x=0.0\mathrm{}$ the system orders antiferromagnetically at $T_N=170\mathrm{}\mathrm{K}.$ At low temperature the system has a canted CE structure. As the temperature approaches $T_N$ there is a transition to a collinear magnetic arrangement. For Sr doping of up to $x=0.15\mathrm{}$ the magnetic transition temperature remains almost constant but the magnetic arrangement now has a ferromagnetic component which persists up to $T_N.$ For $x>\mathrm{}0.15\mathrm{}$ the charge ordering is removed and the lattice parameters show a more normal temperature dependence. The materials are now simple ferromagnets and the ferromagnetic transition temperature $T_C$ increases rapidly with x.