Pressure effects on magnetic and transport properties of electron-doped La_(1-x)Ca_xMnO_3 (x=0.8, 0.9)

摘要

Magnetic and transport properties of polycrystalline La_(1-x)Ca_xMnO_3 (x=0.8,0.9) perovskites were investigated in the temperature range 4.2-300 K, magnetic field up to 16 kOe and under hydrostatic pressures up to 12 kbar. The La_(0.1)Ca_(0.9)MnO_3 compound exhibits a heterogeneous spin configuration in its ground state [G-type antiferromagnetic (AFM) phase with local ferromagnetic (FM) regions and C-type AFM]. The x =0.8 compound is mostly an orbital ordered C-type AFM. In the case of La_(0.1)Ca_(0.9)MnO_3, an applied pressure slightly increases the magnetic transition temperature and significantly enhances the FM component. Pronounced hysteretic effects observed in La_(0.1)Ca_(0.9)MnO_3 may be attributed to the competition between the FM and AFM fractions in the G-AFM structure. On the other hand, La_(0.1)Ca_(0.8)MnO_3 is insensitive to applied pressure probably due to a robustness of orbital ordered state. Resistivity data point out that AFM ordering in occurs at temperatures below orbital ordering.