2.2. BETS Salts with Halometalate Anions 5424 3. Magnetic Metals and Semiconductors 5426 3.1. Mononuclear Metal Complexes 5427 3.1.1. Tetrahalometalates 5427 3.1.2. Hexahalo Anions 5431 3.1.3. Pseudohalide-Containing Anions 5431 3.2. Polynuclear Metal Complexes 5433 3.2.1. Dimeric Anions 5433 3.2.2. Polyoxometalate Clusters 5434 3.3. Chain Anions: Maleonitriledithiolates 5439 4. Ferromagnetic Conductors 5441 5. Ferrimagnetic Insulators 5443 6. Conclusions 5445 7. Acknowledgment 5446 8. References 5446

Magnetic Molecular Conductors

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

During the past 15 years a new field has emerged, which combines superconductivity and spintronics, with the goal to pave a way for new types of devices for applications combining the virtues of both by offering the possibility of long-range spin-polarized supercurrents. Such supercurrents constitute a fruitful basis for the study of fundamental physics as they combine macroscopic quantum coherence with microscopic exchange interactions, spin selectivity, and spin transport. This report follows recent developments in the controlled creation of long-range equal-spin triplet supercurrents in ferromagnets and its contribution to spintronics. The mutual proximity-induced modification of order in superconductor-ferromagnet hybrid structures introduces in a natural way such evasive phenomena as triplet superconductivity, odd-frequency pairing, Fulde-Ferrell-Larkin-Ovchinnikov pairing, long-range equal-spin supercurrents, [Formula: see text]-Josephson junctions, as well as long-range magnetic proximity effects. All these effects were rather exotic before 2000, when improvements in nanofabrication and materials control allowed for a new quality of hybrid structures. Guided by pioneering theoretical studies, experimental progress evolved rapidly, and since 2010 triplet supercurrents are routinely produced and observed. We have entered a new stage of studying new phases of matter previously out of our reach, and of merging the hitherto disparate fields of superconductivity and spintronics to a new research direction: super-spintronics.

https://iopscience.iop.org/article/10.1088/0034-4885/78/10/104501/pdf

Spin-polarized supercurrents for spintronics: a review of current progress.

The many unusual properties of the ternary molybdenum chalcogenides of the type MMo6X8 (M=Metal, X=Chalcogen) are reviewed. Special emphasis is put on the superconducting properties like critical temperature, critical field and the problem of coexistence of magnetism and superconductivity.

Chevrel phases: Superconducting and normal state properties

Vue d'ensemble sur la preparation, la caracterisation, les proprietes de transport et les proprietes magnetiques des superreseaux

Artificial metallic superlattices

The compound ErRh4B4 becomes superconducting at a critical temperature T c1 of 8.7 K followed by a return to the normal state at a second critical temperature T c2 of 0.9 K. The return to the normal state at T c2 is coincident with the occurrence of long-range ordering of the magnetic moments of the Er 3+ ions which completely occupy a set of equivalent lattice sites.

B. T. Matthias

Papers

Destruction of Superconductivity at the Onset of Long-Range Magnetic Order in the Compound ErRh 4 B 4