Intermetallic compounds containing $f$-electron elements display a wealth of superconducting phases, which are prime candidates for unconventional pairing with complex order parameter symmetries. For instance, superconductivity has been found at the border of magnetic order as well as deep within ferromagnetically and antiferromagnetically ordered states, suggesting that magnetism may promote rather than destroy superconductivity. Superconducting phases near valence transitions or in the vicinity of magnetopolar order are candidates for new superconductive pairing interactions such as fluctuations of the conduction electron density or the crystal electric field, respectively. The experimental status of the study of the superconducting phases of $f$-electron compounds is reviewed.

Superconducting phases of f -electron compounds

Thermal properties of metamagnetic transition in heavy-fermion systems

Chapter 1 Magnetism of ternary intermetallic compounds of uranium

Along with pressure and temperature, the magnetic field is one of the physical parameters that are used for the investigation of matter. It is an important tool for investigating magnetic and electronic properties from both the microscopic and macroscopic points of view. The interaction energy of a substance with a magnetic field, i.e. Zeeman energy or Landau energy, is small even at a field of 2 T as can be provided by a conventional electromagnet. Compared with the inner energies of a substance, magnetic fields as high as possible have been required for obtaining fine and detailed information on the internal structure and energy states. Due to the strong Maxwell stress, however, it is quite difficult to obtain a magnetic field higher than 50 T and much effort has been dedicated to the development of magnets ever since the laboratory electromagnet was invented.The purpose of this paper is to describe the physical effects that have been investigated and the phenomena that have been revealed using high magnetic fields, as well as the development of magnet technology and measurement technology. In addition, application to materials processing is mentioned as an active application of high magnetic fields.

https://iopscience.iop.org/article/10.1088/0034-4885/67/11/R02/pdf

Physics in high magnetic fields

The metamagnetic behavior in the heavy-fermion compound YbIr 2 Zn 20 with a cubic structure was studied by magnetization, de Haas–van Alphen (dHvA) oscillation, magnetoresistance, specific heat, thermal expansion, and magnetostriction measurements in single-crystalline samples. A metamagnetic anomaly at H m ≃100 kOe was found to exist in all field directions in the cubic crystal structure. The cyclotron effective mass m c * , the coefficient A in the Fermi liquid relation of electrical resistivity ρ=ρ 0 + A T 2 , and the electronic specific heat coefficient C / T indicate a peak at the metamagnetic field H m . The negative thermal expansion and negative volume magnetostriction suggest that the valence of the Yb ion gradually changes from a 4 f -itinerant state to a trivalent state with increasing magnetic field, and an almost trivalent state is realized above the metamagnetic field H m . On the other hand, the topology of the Fermi surface is approximately unchanged below and above H m in the dHvA experiment.

Metamagnetic Behavior in Heavy-Fermion Compound YbIr2Zn20

The compound SmCo4B is a hard magnetic material; however, the saturation moment and the Curie temperature need to be increased for the compound to be a candidate for a permanent magnetic material. For this purpose, Fe substitution for the Co and Pr substitution for the Sm of SmCo4B have been attempted. In addition, the nitrogenation of SmCo2Fe2 is also attempted. The magnetic characteristics of SmCo2Fe2B have been investigated in a pulsed high magnetic field up to 350 kOe, and the data are compared with those of other related compounds investigated in this work. The compound with more Fe content, SmCo1.7Fe2.3B, has been successfully made, and TC=794 K and saturation moment Ms=81.4 emu/g at 300 K have been obtained. It is found that the Fe substitution does not decrease the uniaxial magnetic anisotropy. Heat treatments in nitrogen gas at 500 °C of SmCo2Fe2B have brought about significant increases of magnetization; however, the increase of TC is only about 20 K and the crystal volume is unchanged to within...

New magnetic material based on SmCo4B

The high field magnetization of antiferromagnetic heavy Fermion material UPd 2 Al 3 is investigated up to 50 T. A clear metamagnetic step is observed at 18 T along the a -axis for 1.3 K. The angular dependence of the step-magnetization shows a large anisotropy in the a c -plane and the spin system can be described by the X Y -spin model except for very small anisotropy in the c -plane. The observed step-magnetization is explained by introducing the model that the heavy Fermion state is broken at the critical field by the magnetic field and the exchange interaction is modified by the change in the carrier density.

High Field Magnetization of UPd2Al3.

We have synthesized several ternary uranium gallides. UNiGa 2 is an enhanced Pauli paramagnet, whereas UPd 2 Ga, UNiGa 3 and UNiGa 4 undergo antiferromagnetic transitions at 6.5, 39 and 42 K, respectively. In UCu 3+ x Ga 2 − x (0.1 ⩽ x ⩽0.8) T N ( x ) assumes a maximum of 17.4 K near x =0.3 and a nonmagnetic heavy-fermion state evolves with further increase in x . Metamagnetic transitions occur in UNiGa 3 , UNiGa 4 and UCU 3.1 Ga 1.9 between 5 and 9 T at 4.2 K.

Structural and physical properties of new U-T-Ga compounds (T=Ni, Cu and Pd)

Metamagnetic transition and phase diagram of a heavy fermion superconductor UPd2Al3

We report on the magnetic, transport, and thermal properties of a heavy-fermion antiferromagnet Ce 7 Ni 3 . The Ce ions in the three nonequivalent sites are found to be very close to trivalent from L III X-ray absorption spectroscopy and magnetic susceptibility measurements. The magnetic susceptibility along the c axis exhibits a pronounced peak at the Neel temperature T N =1.9 K, while that along the b axis defined perpendicular to the a axis shows a rounded maximum at 0.6 K. The magnetization curve for B // c at 1.4 K exhibits a metamagnetic transition at 0.2 T, and reaches a value of 1.0 µ B /Ce at 36 T. The electrical resistivity ρ( T ) for I // c turns up below T N , whereas those for I // a and I // b decrease. These results suggest that the antiferromagnetic order creates a partial gap along the c axis on the Fermi surface. The magnetic entropy due to 4 f electrons reaches 0.47 R ln 2 at T N . The magnetic moment and magnetic entropy in the antiferromagnetic state are substantially reduced by the c...

K. Oda

Papers

New magnetic material based on SmCo4B

High Field Magnetization of UPd2Al3.

Structural and physical properties of new U-T-Ga compounds (T=Ni, Cu and Pd)

Metamagnetic transition and phase diagram of a heavy fermion superconductor UPd2Al3

Magnetic Properties of the Heavy-Fermion Antiferromagnet Ce7Ni3