Magnetic inhomogeneity and magnetotransport in electron-doped Ca1-x Lax Mn O3 (0≤x≤0.10)

The dc magnetization (M) and electrical resistivity (ρ) as functions of magnetic field and temperature are reported for a series of lightly electron doped Ca1-x Lax Mn O3 (0≤x≤0.10) specimens for which magnetization [Phys. Rev. B 61, 14319 (2000)] and scattering studies [Phys. Rev. B 68, 134440 (2003)] indicate an inhomogeneous magnetic ground state composed of ferromagnetic (FM) droplets embedded in a G -type antiferromagnetic matrix. A change in the magnetic behavior near x=0.02 has been suggested to be the signature of a crossover to a long-ranged spin-canted phase. The data reported here provide further detail about this crossover in the magnetization, and additional insight into the origin of this phenomenon through its manifestation in the magnetotransport. In the paramagnetic phase (T≥125 K) we find a magnetoresistance Δρ ρ=-C (M MS) 2 (MS is the low- T saturation magnetization), as observed in many manganites in the ferromagnetic (FM), colossal magnetoresistance (CMR) region of the phase diagram, but with a value of C that is two orders of magnitude smaller than observed for CMR materials. The doping behavior C (x) follows that of MS (x), indicating that electronic inhomogeneity associated with FM fluctuations occurs well above the magnetic ordering transition.