Pressure-induced inhomogeneous chiral-spin ground state in FeGe

Evidence of the Anomalous Fluctuating Magnetic State by Pressure-Driven 4f Valence Change in EuNiGe3

In rare-earth compounds with valence fluctuation, the proximity of the 4f level to the Fermi energy leads to instabilities of the charge configuration and the magnetic moment. Here, we provide direct experimental evidence for an induced magnetic polarization of the Eu³⁺ atomic shell with J = 0, due to intra-atomic exchange and spin-orbital coupling interactions with the Eu²⁺ atomic shell. By applying external pressure, a transition from antiferromagnetic to a fluctuating behavior in EuNiGe₃ single crystals is probed. Magnetic polarization is observed for both valence states of Eu²⁺ and Eu³⁺ across the entire pressure range. The anomalous magnetism is discussed in terms of a homogeneous intermediate valence state where frustrated Dzyaloshinskii-Moriya couplings are enhanced by the onset of spin-orbital interaction and engender a chiral spin-liquid-like precursor.

The hyperfine magnetic fields and the effect of high pressure on the magnetic transition temperatures of the noncentrosymmetric FeRhGe2compound (B20)

Hyperfine parameters and the pressure dependence of the magnetic transition temperatures of FeRhGe₂have been investigated. Sample has been prepared using high pressure-high temperature synthesis technique. FeRhGe₂consists of two B20 structure phases with close lattice constants. The phase separation stays constant in the temperature range 4-300 K. The magnetic transition temperaturesTc1= 213 K andTc2= 135 K of FeRhGe₂slightly increases with pressure in the range 0-4.5 GPa. We have compared this pressure dependence with some others compounds in the family Fe1-xRh_xGe. The two phases in FeRhGe₂have slightly different values of the hyperfine magnetic fields.

Anomalous Nonreciprocal Electrical Transport on Chiral Magnetic Order

Nonreciprocal flow of conduction electrons is systematically investigated in a monoaxial chiral helimagnet CrNb_{3}S_{6}. We found that such directional dichroism of the electrical transport phenomena, called the electrical magnetochiral (EMC) effect, occurs in a wide range of magnetic fields and temperatures. The EMC signal turns out to be considerably enhanced below the magnetic ordering temperature, suggesting a strong influence of the chiral magnetic order on this anomalous EMC transport property. The EMC coefficients are separately evaluated in terms of crystalline and magnetic contributions in the magnetic phase diagram.

Critical phenomenon of the near room temperature skyrmion material FeGe

The cubic B20 compound FeGe, which exhibits a near room temperature skyrmion phase, is of great importance not only for fundamental physics such as nonlinear magnetic ordering and solitons but also for future application of skyrmion states in spintronics. In this work, the critical behavior of the cubic FeGe is investigated by means of bulk dc-magnetization. We obtain the critical exponents (β = 0.336 ± 0.004, γ = 1.352 ± 0.003 and β = 5.276 ± 0.001), where the self-consistency and reliability are verified by the Widom scaling law and scaling equations. The magnetic exchange distance is found to decay as r^−4.9, which is close to the theoretical prediction of 3D-Heisenberg model (r⁻⁵). The critical behavior of FeGe indicates a short-range magnetic interaction. Meanwhile, the critical exponents also imply an anisotropic magnetic coupling in this system.

Solitonic Spin-Liquid State Due to the Violation of the Lifshitz Condition in Fe(1+y)Te

A combination of phenomenological analysis and Mössbauer spectroscopy experiments on the tetragonal Fe(1+y)Te system indicates that the magnetic ordering transition in compounds with higher Fe excess, y≥0.11, is unconventional. Experimentally, a liquidlike magnetic precursor with quasistatic spin order is found from significantly broadened Mössbauer spectra at temperatures above the antiferromagnetic transition. The incommensurate spin-density wave order in Fe(1+y)Te is described by a magnetic free energy that violates the weak Lifshitz condition in the Landau theory of second-order transitions. The presence of multiple Lifshitz invariants provides the mechanism to create multidimensional, twisted, and modulated solitonic phases.