Magnetic and electronic properties of Bi(0.75)Ca(0.25)MnO(3).

The magnetic, structural and electronic properties of Bi(0.75)Ca(0.25)MnO(3) have been investigated in comparison with those of Bi(0.75)Sr(0.25)MnO(3). Magnetometry, diffraction and muon spin relaxation (μSR) data confirm different structural, magnetic and electronic transitions in the two compounds. The anisotropic changes of cell parameters across the structural transition in Bi(0.75)Ca(0.25)MnO(3) (275 K) differ markedly from the lattice anomalies in Bi(0.75)Sr(0.25)MnO(3) (600 K) and also from those in Bi(0.50)Ca(0.50)MnO(3) (325 K). The ground state of Bi(0.75)Ca(0.25)MnO(3) is characterized by a high degree of spin disorder and frustrated interactions. There is no evidence of a ferromagnetic component in the ground state of Bi(0.75)Ca(0.25)MnO(3). However, the application of a magnetic field (even of a few gauss) produces a continuous progressive polarization of the Mn moments (≈2 μ(B)/Mn at 5 T, ZFC, 5 K). Differences between Ca and Sr perovskites with x = 1/4 are greater than for the x = 1/2 counterparts, and point to distinct ground states and charge/orbital configurations.