Dynamical quantum phase transition in XY chains with the Dzyaloshinskii-Moriya and XZY-YZX three-site interactions

We study the dynamical quantum phase transitions (DQPTs) in the XY chains with the Dzyaloshinskii-Moriya interaction and the XZY-YZX type of three-site interaction after a sudden quench. Both the models can be mapped to the spinless free fermion models by the Jordan-Wigner and Bogoliubov transformations with the form $H=\sum_{k}\varepsilon_{k}(\eta^†_{k}\eta_{k}-\frac{1}{2})$, where the quasiparticle excitation spectra $\varepsilon_{k}$ may be smaller than 0 for some $k$ and are asymmetrical ($\varepsilon_{k}\neq\varepsilon_{-k}$). It's found that the factors of Loschmidt echo equal 1 for some $k$ corresponding to the quasiparticle excitation spectra of the pre-quench Hamiltonian satisfying $\varepsilon_{k}\cdot\varepsilon_{-k}<0$, when the quench is from the gapless phase. By considering the quench from different ground states, we obtain the conditions for the occurrence of DQPTs for the general XY chains with gapless phase, and find that the DQPTs may not occur in the quench across the quantum phase transitions regardless of whether the quench is from the gapless phase to gapped phase or from the gapped phase to gapless phase. This is different from the DQPTs in the case of quench from the gapped phase to gapped phase, in which the DQPTs will always appear. Besides, we also analyze the different reasons for the absence of DQPTs in the quench from the gapless phase and the gapped phase. The conclusion can also be extended to the general quantum spin chains.

Atom species energy dependence on magnetic configurations in the perovskite yttrium orthoferrite

The article represents the results of studying of the influence of atom species in the perovskite multiferroic yttrium orthoferrite YFeO3 on magnetic configurations by ab-initio methods. Four magnetic configurations possible in magnetic sublattice that were formed by iron atoms were analyzed. It is shown that different magnetic orderings change the lattice parameters and the ions occupied positions while preserving symmetry of the unit cell, the lowest state responds G-AFM type magnetic ordering. The lattice parameters are in good relevant published experimental data. The atom species energy dependence shows that the main role in magnetic properties goes to iron and oxygen. In the ground state, magnetic properties relate with Dzyaloshinskii – Moriya interaction, while in other configurations, these relate with superexchange through Fe- O-Fe chains. Obtained results are useful for analyzing and designing straintronics devices. Also, the results can be interesting for interpretation and predicting magnetic properties of partially or fully substituted orthoferrites including substitution on rare-earth elements.

Магнитные взаимодействия в структуре фазы Ауривиллиуса Bi-=SUB=-5-=/SUB=-FeTi-=SUB=-3-=/SUB=-O-=SUB=-15-=/SUB=-

This paper analysis the temperature dependence of FC and ZFC magnetization for Bi5FeTi3O15 multiferroic. It has Aurivillius four-layer phase structure. The analysis evidence on the influence of the grains of this material on its overall magnetic properties. The lack of a dramatic temperature threshold in the FC(ZFC) dependences may result in spin canting induced by the Dzyaloshinskii-Moriya interaction.

Observation of temperature-dependent Dzyaloshinskii–Moriya interaction within the 50–300 K range

The Dzyaloshinskii–Moriya interaction (DMI) is essential for the formation of chiral objects in magnetic heterostructures. Herein, the temperature (T)-dependence of the DMI in Pt/Co/MgO is investigated over a wide range below 300 K. The T-dependent behavior of the DMI is stronger than that of the Heisenberg exchange interaction; thus, the anisotropic exchange is more T-sensitive than the isotropic exchange. Additionally, D∝M4.79 and A∝M2 for Pt/Co/MgO, and different ferromagnet (FM) layers can originate from different scaling factors between D and M. Therefore, the DMI T-dependence in a Pt-based multilayer system depends on the FM type, which implies that orbital hybridization at an interface may elucidate the relation between D and M.

Effects of interfacial Dzyaloshinskii–Moriya interaction on magnetic dynamics

In the “Beyond Moore” era, the information device is expected to exhibit advantages including small sizes, high processing speed, and low power and dissipation. The novel magnetic information device with these advantages is made of heavy metal(HM)/ferromagnet (FM) composite. Owing to the asymmetric structure, the anisotropic exchange coupling named the interfacial Dzyaloshinskii–Moriya interaction (iDMI) is generated at the HM/FM interface. This iDMI influences the magnetic dynamics including ferromagnetic resonance (FMR), spin wave, and the motion of chiral DWs. These magnetic dynamic behaviors are the bases of the functions of novel magnetic information devices. Therefore, the influence of iDMI on the magnetic dynamics has attracted wide attention in recent years. In this topical review, we give a detailed introduction and discussion about recent investigation on the iDMI-relevant magnetic dynamics of the HM/FM bilayer system. This review consists of five sections: (1). the introduction about the background, the basic theory of magnetic dynamics and DMI; (2). the review about the effect of iDMI on the propagation of spin wave. Owing to the iDMI, the dispersion relationship of spin wave is asymmetric. This not only offers a precise method for measuring the iDMI constant, but also gives rise to potential application for novel magnonic devices. (3). the review about the effect of iDMI on the FMR. Unique iDMI-relevant mode was observed in the FMR spectra owing to the nonparallel alignment of magnetic moments. (4). the review about the motion of DWs with chiral structure due to iDMI. The iDMI plays a fundamental role in the high velocity of the chiral DWs. Meanwhile, the iDMI results in the tilting of DW plane, and the mechanism has been widely investigated. The tilting of the DW plane may be depressed by the interlayer exchange coupling. (5). finally, we summarize the review and give an outlook.