Neutron scattering studies of an antiferromagnetic Kondo compound: Ce8Pd24Ga

The antiferromagnet Ce8Pd24Ga with TN = 3.1 K has been investigated using neutron diffraction, inelastic neutron scattering, electrical resistivity, magnetoresistance and magnetic susceptibility measurements. Rietveld analysis of neutron diffraction data reveals that Ce8Pd24Ga crystallizes in the cubic structure with space group Pmm. Inelastic neutron scattering (INS) studies show two well-defined crystal-field excitations at 3.2 meV and 12.8 meV. The crystal-field parameters have been estimated from the analysis of INS data. The heat capacity calculated from the crystal-field level scheme shows a Schottky peak at 15 K which agrees well with the reported experimental results. The resistivity exhibits -ln T behaviour at high temperature followed by a peak at 8 K and eventually drops at TN. The peak in the resistivity at 8 K arises due to the combined effect of crystalline electric fields and Kondo interactions. The analysis of the resistivity data in the magnetically ordered state reveals a gap of 16.1 K in the spin-wave spectrum. At 1.8 K the magnetoresistance is positive and it changes to negative at 3 K. The positive magnetoresistance at 1.8 K is consistent with the antiferromagnetic ground state. The negative magnetoresistance shows a scaling behaviour that yields a low-temperature Kondo temperature of 5.8 K. The magnetic susceptibility exhibits Curie-Weiss behaviour between 20 K and 300 K with an effective paramagnetic moment µeff = 2.33 µB and paramagnetic Curie temperature θp = -18.8 K. The present studies reveal that the physical properties of Ce8Pd24Ga are governed by the Kondo, crystal-field and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions.

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