Magnetization and electrical-transport investigation of the dense Kondo systemCeAgSb2

Abstract

Of the dense Kondo materials in the class CeTSb 2 ͑where T = Au, Ag, Ni, Cu, or Pd͒, CeAgSb 2 is special due to its complex magnetic ground state, which exhibits both ferromagnetic and antiferromagnetic character below an ordering temperature T O ϳ 9.8 K. To further elucidate a description of this magnetic ground state, we have carried out a systematic study of single crystalline CeAgSb 2 by magnetic, electrical magneto-transport, and Shubnikov-de Haas ͑SdH͒ studies. We have constructed the magnetic phase diagram based solely on magnetoresistance data. Here, depending on the orientation of the magnetic field H, either ferromagnetic or antiferromagnetic ordering occurs below T O . At zero field the temperature-dependent resistivity below T O is most consistent with antiferromagnetic order, based on the transport theory which includes magnon scattering. The crystal-field-effect theory applied to the susceptibility data yields splitting energies from the ground state to the first and second excited states of 53 K and 137 K, respectively. Based on different models to determine the Kondo temperature T K , we can obtain both low-temperature and high-temperature estimates for T K of ϳ23 K and ϳ65 K, respectively. In the Fermi surface studies, the measurements show very small Fermi surface sections, not predicted by band-structure calculations, and the SdH amplitudes are very sensitive to field direction.

Electronic Structures of Ferromagnetic CeAgSb2: Soft X-ray Absorption, Magnetic Circular Dichroism, and Angle-Resolved Photoemission Spectroscopies

“…Inelastic neutron scattering (INS) experiments and magnetization measurements indicate that the 4f electrons are almost completely localized with an ordered magnetic moment of 0.4 µ B /Ce aligned along the c-axis close to that expected for the CEF doublet ground state Γ 6 of Ce 3+ ions 7,8,[10][11][12] . The magnetic entropy reaching ∼90% of Rln2 at T C , where R is the gas constant, suggests that the Kondo interaction is weaker than the RKKY interaction and the magnetic order develops out of a doublet CEF ground state 7,8,10 .…”

“…Assuming P c = 0.97 21,40 , n f = 1 and an atomic T z / S z ratio of 8/5 38 , we obtained m total = 0.35 ± 0.02 µ B /Ce and m L /m S = −4.05 ± 0.05 from the XAS and XMCD spectra at 6 K. The cutoff energy of p was set to the minimum of the polarization-summed XAS spectrum between the M 5 and M 4 edges and that of q to 940 eV. This m total value is close to the saturation moment of ∼ 0.4µ B /Ce at 1.5 K determined from bulk magnetometry 7,8,[10][11][12] . This provides additional evidence that the localized 4f electrons in the CEF dominate the magnetic properties of CeAgSb 2 .…”

Temperature–field phase diagram of quantum critical CeAuSb2

“…2 . A similar analysis of the magnetoresistivity was performed on the isostructural heavy-fermion system CeAgSb 2 [8], which orders ferromagnetically below T c ¼ 9.6 K. Depending on the field direction the magnon contribution either followed the generic trend for the AFM or FM case. FM ordering along the [0 0 1] www.pss-b.com direction and AFM coupling of the in-plane moments was suggested as a consequence of the anisotropic spin-wave contribution.…”

Hybridization gap in the heavy-fermion compound UPd2Al3 via quasiparticle scattering spectroscopy

“…The upper inset of Fig. 1(b) shows the inverse magnetic susceptibility,  In order to further extract information on the charge transport, we fit the resistivity data in the temperature range between T c and T N to the following expression [29]:…”