Effect of Cu2+ and Ni2+ substitution at the Mn site in (La0.63Ca0.37)MnO3: A neutron powder diffraction investigation

The crystal and magnetic structures of the (La0.63Ca0.37)(Mn1−xTMx)O3 compounds (x=0.00, 0.03, 0.08; TM=Cu2+, Ni2+) were investigated between 5 K and 300 K by means of dc magnetic measurements and neutron powder diffraction analysis followed by Rietveld refinement. Both substituting cations lead to a reduction of the long range ferromagnetic ordering temperature; ferromagnetism is strongly suppressed in the 8% Cu-substituted sample, where long- and short-range FM magnetic orders coexist together with short-range A-type AFM order. This particular feature can be related to the Jahn–Teller character of Cu2+, absent in Ni2+, and suggests the occurrence of a quantum critical point in the (La0.63Ca0.37)(Mn1−xCux)O3 system.