Antiferromagnetic and ferromagnetic spintronics and the role of in-chain and inter-chain interaction on spin transport in the Heisenberg ferromagnet

Spin-transport and current-induced torques in ferromagnet heterostructures given by a ferromagnetic domain wall are investigated. Furthermore, the continuum spin conductivity is studied in a frustrated spin system given by the Heisenberg model with ferromagnetic in-chain interaction $$J_1<0$$ J 1 < 0 between nearest neighbors and antiferromagnetic next-nearest-neighbor in-chain interaction $$J_2>0$$ J 2 > 0 with aim to investigate the effect of the phase diagram of the critical ion single anisotropy $$D_c$$ D c as a function of $$J_2$$ J 2 on conductivity. We consider the model with the moderate strength of the frustrating parameter such that in-chain spin-spin correlations that are predominantly ferromagnetic. In addition, we consider two inter-chain couplings $$J_{\perp ,y}$$ J ⊥ , y and $$J_{\perp ,z}$$ J ⊥ , z , corresponding to the two axes perpendicular to chain where ferromagnetic as well as antiferromagnetic interactions are taken into account.

Information dynamics in a model with Hilbert space fragmentation

The fully frustrated ladder – a quasi-1D geometrically frustrated spin one half Heisenberg model – is non-integrable with local conserved quantities on rungs of the ladder, inducing the local fragmentation of the Hilbert space into sectors composed of singlets and triplets on rungs. We explore the far-from-equilibrium dynamics of this model through the entanglement entropy and out-of-time-ordered correlators (OTOC). The post-quench dynamics of the entanglement entropy is highly anomalous as it shows clear non-damped revivals that emerge from short connected chunks of triplets. We find that the maximum value of the entropy follows from a picture where coherences between different fragments co-exist with perfect thermalization within each fragment. This means that the eigenstate thermalization hypothesis holds within all sufficiently large Hilbert space fragments. The OTOC shows short distance oscillations arising from short coupled fragments, which become decoherent at longer distances, and a sub-ballistic spreading and long distance exponential decay stemming from an emergent length scale tied to fragmentation.

Enhanced Magnetization in a Frustrated Spin System by Ni+ Ion Beam Irradiation

We investigate the magnetic properties in a frustrated spin system of carbonyl iron (CI) particles before and after Ni+ ion beam irradiation. Upon increasing temperatures, the saturation magnetization exhibits an anomalous increase, which is more intense after the beam irradiation. The zero-field cooled (ZFC) magnetization data show an anomalous increase up to 300 K, regardless of the beam irradiation. After the irradiation, unlike in the unirradiated CI particles, the ZFC curve shows separated regimes, reflecting two distributions of the blocking temperature, which may be related to the particle distribution summed with two distribution functions. After the irradiation, strong interparticle interaction may be present due to the effect of dipolar interaction among CI particles doped Ni ions, leading to the enhanced magnetization. We may suggest that the anomalous magnetization behavior can be ascribed to frustration in the internal magnetic order for the unirradiated CI particles, and further interparticle interaction for the irradiated CI particles.

Quantum phases and spin liquid properties of 1T-TaS2

Quantum materials exhibiting magnetic frustration are connected to diverse phenomena, including high Tc superconductivity, topological order, and quantum spin liquids (QSLs). A QSL is a quantum phase (QP) related to a quantum-entangled fluid-like state of matter. Previous experiments on QSL candidate materials are usually interpreted in terms of a single QP, although theories indicate that many distinct QPs are closely competing in typical frustrated spin models. Here we report on combined temperature-dependent muon spin relaxation and specific heat measurements for the triangular-lattice QSL candidate material 1T-TaS2 that provide evidence for competing QPs. The measured properties are assigned to arrays of individual QSL layers within the layered charge density wave structure of 1T-TaS2 and their characteristic parameters can be interpreted as those of distinct Z2 QSL phases. The present results reveal that a QSL description can extend beyond the lowest temperatures, offering an additional perspective in the search for such materials.