Magnetization and magnetic phases in metallic and semiconducting Ho_xCa_<1-x>MnO_3

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We have measured the magnetization, susceptibility, specific resistance, X-ray and neutron diffraction data of the series Ho_xCa_<1-x>MnO_3 (x<__-0.5; step width Δx=0.1 or less). The compounds analyzed have distorted perovskite structures: they are orthorhombic for 0<__-x<__-0.13, and have an orthorhombic to monoclinic phase transition for 0.13<__-x<__-0.33. Ho ions are paramagnetic for 4 K<__-T<__-300 K. Their magnetization and susceptibility at low temperatures are, however, reduced from what one expects for free ions. We calculate a crystal field correction M_<H0> (T,H) and x_<H0> (T). The resulting data for Mn show a reduced magnetic moment (x>__-0.2) and a ferromagnetic phase at x= 0.1±0.05 with ordering temperatures T_N/T_C〓110 K.These results show that (Ho_xCa_<1-x>)MnO_3 belongs to the family of the giant magnetoresistance compounds (La_xCa_<1-x>)MnO_3 with, however, the ferromagnetic phase occuring at x=0.1 as compared to x=0.67 in the La-compound.
社団法人日本磁気学会の論文
1999-01-20