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Anomalous Transport and Thermal Properties of the Solid Solutions U_{1-x}Th_{x}Cu_{5}M (M = Al, Ga, In and Sn)

100%

Troć R., Tran V., Kaczorowski D., Czopnik A.

Acta Physica Polonica A

2000

vol. 97

issue 1

25-35

UCu_{5}M-type compounds are moderate heavy fermion systems with an antiferromagnetic order below T_{N} = 18, 16-25, and 25 K for M = Al, (Ga, In), and In, respectively, and a ferrimagnetic order with T_{C} = 54 K for M = Sn. We present the results of magnetoresistance measurements as a function of temperature and applied magnetic field for the pure compounds and for their solid solutions containing Th, i.e. U_{1-x}Th_{x}Cu_{5}M. Only in the case of UCu_{5}In a substantial positive contribution to the magnetoresistance was observed at low temperatures, as for normal antiferromagnets. For the Al- and Sn-based alloys the magnetoresistance at low temperatures is negative, and its field variation proves the existence of Kondo-type interactions. On Th-substitution the magnetic phase transition is shifted to lower temperature and simultaneously the magnetoresistance becomes less negative. The field dependence of the magnetoresistance of these alloys can be well described by the Coqblin-Schrieffer model. Interestingly, the heat capacity measurements have revealed a general tendency to increase the linear coefficient γ with magnetic dilution of a given UCu_{5}M compound by Th-substitution. This feature reflects an enlargement of the effective mass of conduction electrons with the increase in both the unit cell volume and magnetic dilution. Such a tendency is also observed for the system UCu_{5}(In_{1-x}Ga_{x}), though the unit cell is here suppressed with increasing x. Thus, a similar physical picture is reached in all these systems but involving probably different mechanisms.

f-Electron Behavior in Rare Earth Based Systems: Localization or Itinerancy?

100%

Biasini M., Rusz J., Ferro G., Czopnik A.

Measurement of the two-dimensional angular correlation of the electron-positron annihilation radiation complemented with ab initio calculations can provide decisive information about the character of the f-electrons in rare earth compounds. We provide examples of f-electron localized and f-electron itinerant systems, respectively. (i) In the case of the antiferromagnetic heavy fermion and superconductor CeIn_3 the multisheet Fermi surface, reconstructed from our measurements in the paramagnetic phase, agrees closely with the predictions of band structure calculations regarding the Ce 4f electrons as fully localized. (ii) On the other hand, our studies of the antiferromagnet actinide based UGa_3 in the paramagnetic phase, compared with calculations which include the effects due to the non-uniform positron density and the electron-positron correlations, produce a substantial evidence that an unconstrained 5f-electron itinerant description applies.

Anomalous Diamagnetism of YbPb_3 Compound: Pressure Effects

76%

Baranovskiy A., Grechnev G., Panfilov A., Svechkarev I., Żogał O., Czopnik A., Hackemer A.

Acta Physica Polonica A

2008

vol. 113

issue 1

243-246

The effect of a uniform pressure on the magnetic susceptibility was measured for YbPb_3 compound, wherein a degeneracy point of the energy bands is located just below the Fermi level and responsible for the anomalous diamagnetism. Theoretical analysis of the experimental data has revealed that a pronounced increase of diamagnetism with pressure is governed by closing the degeneracy point towards the Fermi energy

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3 Acta Physica Polonica A

1 2008

1 2005

1 2000

3 Czopnik A.

1 Baranovskiy A.

1 Biasini M.

1 Ferro G.

1 Grechnev G.

1 Hackemer A.

1 Kaczorowski D.

1 Panfilov A.

1 Rusz J.

1 Svechkarev I.

1 Tran V.

1 Troć R.

1 Żogał O.

Search results

Anomalous Transport and Thermal Properties of the Solid Solutions U_{1-x}Th_{x}Cu_{5}M (M = Al, Ga, In and Sn)

f-Electron Behavior in Rare Earth Based Systems: Localization or Itinerancy?

Anomalous Diamagnetism of YbPb_3 Compound: Pressure Effects