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(La 1- x Y x )Mn 4 Al 8 (0 ≤ x ≤1) is a very unique itinerant electron system, in which the spin pseudogap can be controlled continuously and nearly uniformly in a wide range of the gap width from Δ≃250 to 500 K by the anisotropic volume shrinkage induced by the chemical pressure. The hydrostatic pressure on LaMn 4 Al 8 also increases Δ but tends to fill the gap. The strong and anisotropic volume dependence of Δ strongly supports the idea that the origin of the gap formation is associated with the one-dimensional geometry of the Mn spin arrangement.

The electron correlation in the 3d heavy-electron compound with linear spin chains, LaMn 4 Al 8 , has been investigated. Like a similar compound, YMn 4 Al 8 , we found a broad maximum in the temperature dependence of the susceptibility. This is interpreted by assuming the presence of a narrow pseudogap with the width Δ≃280 K in the spin excitation spectrum, which leads to the quenching of spin at low temperatures. Anomalies in susceptibility, resistivity and thermal expansion data, observed below approximately 50 K in spite of the absence of any phase transition, suggest the recovery of spin and the development of short-range magnetic correlation in this low-temperature range. This is in contrast to the case of YMn 4 Al 8 . No apparent long-range ordering in spite of the markedly developed magnetic correlation is probably due to the one-dimensional nature of the Mn spin arrangement.

Experimental results of the susceptibility, the Knight shift and the nuclear spin–lattice relaxation rate suggest that the tetragonal intemetallic compound with linear chains of Mn atoms, YMn 4 Al ...

We performed muon spin relaxation (µSR) experiments on a \(S =\frac{1}{2}\) triangular lattice system, BaVS 3 . Fast muon spin relaxation was observed below T X ≃30 K, indicating magnetic ordering....

Magnetic and transport properties of ferromagnetic BaVSe 3 (the Curie temperature T C ≃43 K) were investigated. The resistivity shows metallic behavior. The saturation magnetization in the ferromagnetic state is homogeneously reduced to 0.34 µ B /f.u. in contrast to the large paramagnetic moment 1.42 µ B /f.u.; the nearly full moment value for a local spin 1/2. NMR experiments revealed a single magnetic V site below T C . Although the macroscopic magnetic properties of BaVSe 3 is similar to those of sulfur-deficient BaVS 3-δ , BaVSe 3 is characterized by the itinerant electron magnetism in contrast to more ionic characters of the BaVS 3 system.

We performed powder neutron diffraction and scattering experiments of the \(S = \frac{1}{2}\) triangular lattice system, BaVS 3 , and found magnetic reflections below T X ≃30 K. The propagation vector is determined to be incommensurate (0.226 0.226 0) in the hexagonal index. The ordered moment is roughly estimated to be ∼0.5 µ B /V. Although the elastic magnetic diffractions disappear above T X , low-energy inelastic scattering, which has an Q -ω dispersion similar to that below T X , was observed between T X and the metal-insulator transition point T MI ≃70 K, indicating the presence of a long-range and dynamic antiferromagnetic correlation, i.e., a spin-liquid-like state, between T X and T MI .