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1

Anomalous Superconductivity and Antiferromagnetism in the U(Pt,Pd)_3 System

100%

Franse J.

Acta Physica Polonica A

|

2001

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vol. 100

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issue Supplement

153-176

EN

A review is presented of the anomalous magnetic and superconducting properties of the heavy-fermion compound UPt_3 that has been a subject of extensive study during the past twenty years. The normal-state and superconducting properties of the compound were evaluated from magnetic, transport, and thermodynamic studies. In addition, neutron-diff raction and muon spin relaxation experiments were performed in the normal and superconducting states. The compound is characterized by a multiple superconducting phase diagram and by the coexistence of superconductivity and short-range antiferromagnetic interactions with quasi-static moments of the order of 10^{-2}μ_B/U-atom. Upon substituting Pt by Pd, the short-range magnetic interactions give way to long-range antiferromagnetic order with a maximal ordering temperature of 6 K for the 5 at.% Pd alloy and a magnetic moment of 0.6μ_B/U-atom. Superconductivity and long-range antiferromagnetic order are in competition resulting in a critical composition of 0.6 at.% Pd. At this concentration, non-Fermi liquid behaviour is observed.

2

Stark and Zeeman Effects in Nd_{2}Fe_{14}B and Pr_{2}Fe_{14}B Intermetallics

63%

Radwański R., Franse J.

Acta Physica Polonica A

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1996

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vol. 90

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issue 1

223-232

EN

The energy level scheme of the Nd^{3+} and Pr^{3+} ions in ferromagnetic Nd_{2}Fe_{14}B and Pr_{2}Fe_{14}B intermetallic compounds was evaluated on the basis of all known experiments. In calculations the effect of charge (Stark effect) and spin-dependent (Zeeman effect) interactions were taken into account by means of the crystal-field and molecular-field approximation, respectively. The derived energy level scheme is associated with the removal of the degeneracy of the lowest multiplet given by Hund's rules, i.e. ^{4}I_{9/2} (Nd^{3+}) and ^{3}H_{4} (Pr^{3+}). The revealed low-energy electronic structure (<25 meV = 200 cm^{-1}) is associated with many-electron states of the RE^{3+} ions. Magnetic and electronic properties resulting from this fine structure are compared with all known experimental results. The localized crystal electric field levels exist also in Nd_{2}CuO_{4}, an ionic compound which by doping with Ce becomes high-T_{c} superconductor, indicating the formation of crystal electric field states independently on the metallic or ionic state.

3

Effect of Spin Reorientational Transition on Magnetoresistivity of Noncolinear Ferromagnet U_{3}As_{4}

51%

Bakker K., Wiśniewski P., Henkie Z., Franse J.

Acta Physica Polonica A

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1994

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vol. 85

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issue 2

245-248

EN

Transverse magnetoresistivity (H ∥ [001]; and current ∥ [110]) of U_{3}As_{4} has been measured in field up to 35 T. An abrupt change of the magnetoresistivity behaviour from saturated (low field) to unsaturated (high field) type was observed at the spin reorientational transition (19.1 T at 4.2 K). The transition is accompanied by a peak in the magnetoresistivity. The behaviour is ascribed to fractional spin polarization of the band electrons.

4

Specific Heat of RBa_{2}Cu_{3}O_{7-x} and RBaSrCu_{3}O_{7-x} Compounds (R = Sm, Dy, Er)

45%

Tarnawski Z., Kim-Ngan N., Wang X., Duijn V., Franse J.

Acta Physica Polonica A

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1998

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vol. 93

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issue 3

513-522

EN

The low-temperature specific-heat C(T) data of high-T_{c} superconductors RBa_{2}Cu_{3}O_{7-x}(R123O_{7-x}) were reviewed. A discussion of the C(T) data obtained on single-crystalline samples of Er123O_{7-x} and Sm123O_{7-x} compounds in applied magnetic fields for better evaluation of the crystal-electric-field parameters is given. The C(T) measurements of Sr-substituted compounds RBaSrCu_{3}O_{7} revealed the λ-type of peak related to the antiferromagnetic order at 1.2 K and 0.6 K respectively for Dy- and Er-compounds. The magnetic singlet ground state in these compounds is produced by weak exchange interactions of -0.05 T/μ_{B} and -0.035 T/μ_{B}, respectively. For Nd- and Sm-compounds, only a broad anomaly around 0.6 K was observed which is well fitted with a Schottky-type anomaly with an energy splitting of 1.4 K.

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4 Acta Physica Polonica A

1 2001

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4 Franse J.

1 Bakker K.

1 Duijn V.

1 Henkie Z.

1 Kim-Ngan N.

1 Radwański R.

1 Tarnawski Z.

1 Wang X.

1 Wiśniewski P.

Anomalous Superconductivity and Antiferromagnetism in the U(Pt,Pd)_3 System

Stark and Zeeman Effects in Nd_{2}Fe_{14}B and Pr_{2}Fe_{14}B Intermetallics

Effect of Spin Reorientational Transition on Magnetoresistivity of Noncolinear Ferromagnet U_{3}As_{4}

Specific Heat of RBa_{2}Cu_{3}O_{7-x} and RBaSrCu_{3}O_{7-x} Compounds (R = Sm, Dy, Er)