M. Sera

Ce- and Yb-based Kondo semiconductors

Abstract Kondo semiconductors are a class of strongly correlated f-electron materials whose low-energy excitations exhibit a (pseudo)gap at low temperatures. The significant difference between the pseudogap in orthorhombic CeNiSn and CeRhSb and the real gap in cubic Ce 3 Bi 4 Pt 3 and YbB 12 is highlighted by a comparison of transport properties. Low-temparature measurements of the magnetoresistance, Hall coefficient and specific heat of CeNiSn have revealed a field-induced excitation of the coherent low-carrier state. A systematic study of CeNi 1− x T x Sn ( T = Co, Cu and Pt ) has shown that the residual carriers in CeNiSn are immobilized by 1% substitution irrespective of the substitutes. Further substitution with 5% Cu induces a magnetic instability at T = 0.

DE Haas-van Alphen effects on La(Sb, Bi) and Ce(Sb, Bi)

Abstract De Haas-van Alphen effects on LaSb and CeSb were measured. The calculated energy band structure in LaSb agrees with the experimental results. Experimental results of CeSb support strongly the p-f mixing theory.

Quadrupolar ordering and dense kondo behaviour in SmSn3

Abstract From the specific heat measurement on SmSn 3 , it is found that the ground state of Sm 3+ ( J = 5 2 ) ions is Γ 8 quartet and that the magnetic phase transition at T N ≈ 10 K reported so far is not simple but of successive transitions due to probably quadrupolar ordering. We also observed that SmSn 3 exhibits dense Kondo behaviour. These results are compared with our experimental results on isomorphous compound SmIn 3 .

Antiferromagnetic Ordering in the Spin Singlet State of the Ladder/Chain Material: Sr2.5Ca11.5Cu24O41

We report on specific heat and neutron scattering measurements performed for Sr 14- x Ca x Cu 24 O 41 single crystals. The specific heat data of Sr 2.5 Ca 11.5 Cu 24 O 41 showed a sharp phase transition at T N ≈2.1 K, indicating the possible onset of a long-range order. Specific heat measurements under magnetic fields also revealed that this phase transition is not due to charge ordering or structural phase transition but to magnetic ordering. In the neutron scattering experiments, we observed several Bragg peaks, corresponding to the magnetic ordering observed in the specific heat measurements. Furthermore, we confirmed from polarized neutron scattering measurements that these Bragg peaks are undoubtedly magnetic in origin. Considering both the nuclear magnetic resonance and neutron scattering data, a possible magnetic structure on the chain and ladder sites has been proposed. In this system, the singlet state and antiferromagnetic order induced by appropriate hole-doping coexist at ambient pressure and ...

On the crystal field and Kondo effect in CeIn3

Abstract Specific heat, electrical resistivity, Hall effect, elastic constant and magnetization were studied in CeIn 3 single crystals. In this process, we found anomalous samples, some of them showed superconductivity with T c = 6 K .

Magnetic and transport properties of anomalous Ce-monopnictides

Abstract The x dependence of the crystal field splitting Δ 8 7 obtained from thermal expansion measurements of Ce 1− x La x Sb and Ce 1− x La x Bi is consistent with the p-f(Γ 8 ) mixing model. The Hall effect shows that the current is carried by 5d(t 2g ) conduction electrons and the observed Kondo-like behavior of the resistivity is explained by the formation of a Kondo state due to d-f(Γ 7 ) mixing.

Crystalline field and kondo effect in CeBi1-xTex

Abstract Magnetic and transport properties on CeBi 1- x Te x solid solution are reported. For 0.125 ≲ x ≲ 0.3, the long range magnetic ordering seen for x ⩽ 0.1 diappears and the spin glass freezing is observed. The crystal field splitting for x ⩾ 0.1 is estimated to be ≈ 40 K with Г 7 ground state from the thermal dilation. These are well explained within the p-f mixing model.

MAGNETIC AND TRANSPORT PROPERTIES OF KONDO COMPOUND α-Ce3Al

Abstract We have measured the magnetic and transport properties of α-Ce 3 Al. Two characteristics anomalies are observed around 100 and 3 K with a resistance minimum around 20 K. The high-temperature anomaly may be due to some kind of transition accompanying a gap on parts of the Fermi surface. The low-temperature anomaly originates from the antiferromagnetically ordering with a reduced ordered moment.

Magnetoelastic studies on Ce1−xLaxB6 single crystals

Abstract The thermal dilatations and magnetostrictions of Ce 1− x La x B 6 single crystals under both longitudinal and transverse magnetic field show systematic but drastic variations. These results suggest, for CeB 6 , the splitting of the Γ ∗ quartet ground state in the paramagnetic region and the reduction of the antiferroquadrupolar component in Phase II in zero magnetic field which is enhanced by the magnetic field.

Cu site substitution effect on the Hall coefficient of La2-xSrxCuO4

The Cu site substitution effects on the Hall coefficient RH and the electrical resistivity ϱ have been studied for La2−xSrxCuO4. In a small x region, RH decreases largely with Zn doping and increases with Ni doping. In the Ni doped samples, ϱ shows the characteristic temperature dependence similar to those of the unsubstituted samples where the decrease of the slope of ϱ vs. T curve is observed for x<0.1 above ∼600K but in the Zn doped samples, the change of the slope of ϱ becomes smaller,i.e. the temperature dependence of ϱ below ∼600K becomes smaller. These results indicate that the origin of the change of the slope of ϱ around 600K for x<0.1 is magnetic and the spin correlation or the electronic state is rather different below and above ∼600K. The unusual Zn doping dependences of RH and ϱ are naturally explained by considering that the electronic state at high temperatures above ∼600K which has a small Hall coefficient expected for the large Fermi surface comes down to lower temperatures by the Zn doping.