Study of Novel Magnetic Phases in Vanadium Sulfide Single Crystals
Strongly correlated electron systems are known to give rise to a variety of exotic properties and new quantum phases, such as non-Fermi liquids, high-temperature superconductors, heavy-fermion systems and quantum spin liquids. Transition metal chalcogenides such as the vanadium sulphides, V_xS_8, show an extremely broad variety of physical phenomena that can strongly depend on stoichiometry and purity. Structural, magnetic, and charge-density wave phase transitions may occur upon varying the temperature, pressure or chemical composition x. These compounds are interesting since the character of the d-electrons varies widely depending on x, ranging from weak itinerant-electron antiferromagnetism to considerably localized-electron antiferromagnetism. The focus of this work is in the weak itinerant antiferromagnets, in which the Néel temperature may be tuned to a quantum phase transition by applying hydrostatic pressure. As such, they are candidates to exhibit non-Fermi liquid behaviour and magnetically mediated superconductivity, where electrons are paired in a finite angular momentum state. Also, new magnetic phases can emerge in high purity single crystals of the compound V5S8 with high magnetic fields applied, being possible to prepare a magnetic phase diagram for the compound under study.