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The ternary alloy Ag–In–Ce is the only Ce-based quasicrystal approximant showing the heavy fermion feature. Here, we report the physical properties of Ag–In–(CexY1−x). As the Ce concentration x is diluted by the nonmagnetic element Y, the spin glass freezing temperature Tf is progressively suppressed. At T > Tf, the uniform magnetic susceptibility and electronic specific heat coefficient show \(\chi (T,x)^{ - 1} = \alpha [T^{\zeta } + \theta _{\text{eff}}^{\zeta }(x)]\) (where α is a constant, ζ \(\simeq \) 0.7, and θeff is an effective Weiss temperature) and \(C(T,x)/T = \beta \ln [T/T_{0}(x)]\) (where β is a constant and T0 is a characteristic temperature), respectively. Near the critical concentration xc where θeff vanishes, χ and C/T exhibit power-law and logarithmic divergence, respectively, as T → 0. We stress that α, ζ, and β are independent of x, indicating that the Tζ and ln T terms come from local fluctuations that are present everywhere in the x–T phase diagram, regardless of quantum critical point. We argue that the quantum critical behavior is driven by valence fluctuations. [ABSTRACT FROM AUTHOR]

The Ag–In–Ce alloy is an approximant crystal to a Tsai-type quasicrystal and exhibits heavy-fermion (Kondo) physics. This new type of Kondo material exhibits spin-glass ordering below the freezing temperature Tf ∼ 0.3 K at ambient pressure. Here we investigated the effect of hydrostatic pressure on the Ag–In–Ce alloy. Spin-glass features, such as the frequency-dependent cusp near Tf in the ac magnetic susceptibility curve, were observed even under external pressure. In addition, the C/T value (where C is the specific heat) increased with decreasing temperature and exhibited a broad peak above Tf. The Tf increased as the pressure increased up to its highest value in the experiment (approximately 2.6 GPa). [ABSTRACT FROM AUTHOR]

Investigations of reaction mixtures RE x (Au 0.79 Si 0.21 ) 100- x (RE = Y and Gd) yielded the compounds REAu 3 Si which adopt a new structure type, referred to as GdAu 3 Si structure ( tP 80, P 4 2 / mnm , Z = 16, a = 12.8244(6)/12.7702(2) Å, and c = 9.0883(8)/9.0456(2) Å for GdAu 3 Si/YAu 3 Si, respectively). REAu 3 Si was afforded as millimeter-sized faceted crystal specimens from solution growth employing melts with composition RE 18 (Au 0.79 Si 0.21 ) 82 . In the GdAu 3 Si structure, the Au and Si atoms are strictly ordered and form a framework built of corner-connected, Si-centered, trigonal prismatic units SiAu 6 . RE atoms distribute on 3 crystallographically different sites and each attain a 16-atom coordination by 12 Au and 4 Si atoms. These 16-atom polyhedra commonly fill the space of the unit cell. The physical properties of REAu 3 Si were investigated by heat capacity, electrical resistivity, and magnetometry techniques and are discussed in the light of theoretical predictions. YAu 3 Si exhibits superconductivity around 1 K, whereas GdAu 3 Si shows a complex magnetic ordering, likely related to frustrated antiferromagnets exhibiting chiral spin textures. GdAu 3 Si-type phases with interesting magnetic and transport properties may exist in an extended range of ternary RE-Au-Si systems, similar to the compositionally adjacent cubic 1/1 approximants RE(Au,Si) ∼6 .

Topological spin structures such as magnetic domain walls, vortices, and skyrmions, have been receiving great interest because of their high potential application in various spintronic devices. To utilize them in the future spintronic devices, it is first necessary to understand the dynamics of the topological spin structures. Since inertial effect plays a crucial role in the dynamics of a particle, understanding the inertial effect of topological spin structures is an important task. Here, we report that a strong inertial effect appears steadily when a skyrmion is driven by an oscillating spin-Hall-spin-torque (SHST). We find that the skyrmion exhibits an inertia-driven hypocycloid-type trajectory when it is excited by the oscillating SHST. This motion has not been achieved by an oscillating magnetic field, which only excites the breathing mode without the inertial effect. The distinct inertial effect can be explained in terms of a spin wave excitation in the skyrmion boundary which is induced by the non-uniform SHST. Furthermore, the inertia-driven resonant excitation provides a way of experimentally estimating the inertial mass of the skyrmion. Our results therefore pave the way for the development of skyrmion-based device applications.

We theoretically investigate the dynamics of antiferromagnetic domain walls driven by spin-orbit torques in antiferromagnet-heavy-metal bilayers. We show that spin-orbit torques drive antiferromagnetic domain walls much faster than ferromagnetic domain walls. As the domain wall velocity approaches the maximum spin-wave group velocity, the domain wall undergoes Lorentz contraction and emits spin waves in the terahertz frequency range. The interplay between spin-orbit torques and the relativistic dynamics of antiferromagnetic domain walls leads to the efficient manipulation of antiferromagnetic spin textures and paves the way for the generation of high frequency signals from antiferromagnets.