Ferromagnetism vs Paramagnetism and False Quantum Oscillations in Lanthanum-Doped CaB_6 : Condensed Matter: Electronic Properties, etc.

概要

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Magnetization and resistivity were measured as functions of temperature and magnetic field on two single crystals of C_aB_6 and three of (Ca_<0.995>La_<0.005>)B_6. One of the doped crystals exhibited ferromagnetism with the magnetic moment of 0.32 μB/La at 10kOe and 5 K, while the other two were paramagnetic, displaying the Curie law below 120 K with the effective magnetic moment of 1.3 or 2.0μB/La. We propose that the sample-dependent magnetic behaviors of (Ca_<0.995>La_<0.005>)B_6 may be explained in terms of superparamagnetism, assuming that the ferromagnetic state is spatially inhomogeneous. All the samples exhibited the metallic behavior of electrical conduction. Quantum oscillations were found in the magnetoresistance of one of the doped crystals. The angular dependence of the oscillations, however, indicates that their origin is not the sample bulk.
社団法人日本物理学会の論文
2000-08-15