Easy Plane Research Articles

Effects of orientation methods on electromagnetic parameters and microwave absorption characteristics of flaky carbonyl iron@SiO2 particles

In this study, flaky carbonyl iron powder (CIP)@SiO2 particle/polyurethane (PU) composites with different steric configurations were prepared using a rotating magnetic field and different cutting methods. The effects of the angle between the easy magnetization plane and the vector of incident electromagnetic (EM) waves on the EM parameters and microwave absorption characteristics were studied. In order to investigate the influences of different steric configurations of the flaky CIP@SiO2 particles on the EM parameters of the composites, the complex permeability of the samples was calculated using the Landau-Lifshitz-Gilbert equation and Bruggeman’s effective medium theory combined with consideration of the shape anisotropy. The calculated results agreed well with the experimental results. In addition, it was revealed that the complex permeability of the composites was dominated mainly by the steric configuration of the flaky CIP@SiO2 particles, which was significant for the development of an excellent absorber in oblique incident conditions.

Effective-Field Approach to Long-Range Order of Spin-1 and Spin-1/2 Mixed System in XXZ Model with Single-Ion Uniaxial Anisotropy

In the XXZ Heisenberg model with the positive single-ion uniaxial anisotropy D, where the xy-plane is the easy plane of magnetization, the substitution effect of spin-1/2 for a spin-1 system is exp...

Anisotropy-Induced Soliton Excitation in Magnetized Strong-Rung Spin Ladders.

We report low temperature electron spin resonance experimental and theoretical studies of an archetype S=1/2 strong-rung spin ladder material (C_{5}H_{12}N)_{2}CuBr_{4}. Unexpected dynamics is detected deep in the Tomonaga-Luttinger spin liquid regime. Close to the point where the system is half-magnetized (and believed to be equivalent to a gapless easy plane chain in zero field) we observed orientation-dependent spin gap and anomalous g-factor values. Field theoretical analysis demonstrates that the observed low-energy excitation modes in magnetized (C_{5}H_{12}N)_{2}CuBr_{4} are solitonic excitations caused by Dzyaloshinskii-Moriya interaction presence.

Higher-order crystal field and rare-earth magnetism in rare-earth– Co5 intermetallics

Crystal-field (CF) effects on the rare-earth (RE) ions in ferrimagnetic intermetallics NdCo$_5$ and TbCo$_5$ are evaluated using an ab initio density functional + dynamical mean-field theory approach in conjunction with a quasi-atomic approximation for on-site electronic correlations on the localized 4$f$ shell. The study reveals an important role of the high-order sectoral harmonic component of the CF in the magnetism of RECo$_5$ intermetallics. An unexpectedly large value is computed in the both systems for the corresponding crystal-field parameter (CFP) $A_6^6 \langle r^6 \rangle$, far beyond what one would expect from only electrostatic contributions. It allows solving the enigma of the non-saturation of zero-temperature Nd magnetic moments in NdCo$_5$ along its easy axis in the Co exchange field. This unsaturated state had been previously found out from magnetization distribution probed by polarised neutron elastic scattering but had so far remained theoretically unexplained. The easy plane magnetic anisotropy of Nd in NdCo$_5$ is strongly enhanced by the large value of $A_6^6\langle r^6 \rangle$. Counter-intuitively, the polar dependence of anisotropy energy within the easy plane remains rather small. The easy plane magnetic anisotropy of Nd is reinforced up to high temperatures, which is explained through $J$-mixing effects. The calculated ab initio anisotropy constants of NdCo$_5$ and their temperature dependence are in quantitative agreement with experiment. Unlike NdCo$_5$, the $A_6^6 \langle r^6 \rangle$ CFP has negligible effects on the Tb magnetism in TbCo$_5$ suggesting that its impact on the RE magnetism is ion-specific across the RECo$_5$ series. The origin of its large value is the hybridization of RE and Co states in a hexagonally coordinated local environment of the RE ion in RECo$_5$ intermetallics.

Domain walls in antiferromagnets: The effect of Dzyaloshinskii–Moriya interactions

We investigate domain walls in antiferromagnets focusing on the effect of Dzyaloshinskii–Moriya interactions (DMIs). Using spin model simulations and analytical arguments within a continuum theory, we show that Dzyaloshinskii–Moriya interactions affect static as well as dynamic properties of the domain wall. For certain configurations of the DMI vectors, the DMI can either tilt the easy plane of the domain wall, an effect that leads to a reduced domain wall width, or it can favor a certain chirality of the domain wall. Depending on the DMI configuration, the DMI may lead to an increasing or decreasing domain wall velocity. The asymmetry of the domain wall velocity observed in ferromagnets subject to DMI cannot be found in antiferromagnetic systems.

Electronic Structure and Magnetic Anisotropy of Single-Layer Rare-Earth Oxybromide.

The discovery of intrinsic magnetism in two-dimensional (2D) limit has triggered increasing investigations in layered magnetic materials. However, most of the available candidates involves 3d transition metals, while the layered rare-earth magnetic materials are largely unexplored at present. Here, we proposed a series of 2D rare-earth magnetic semiconductors REOBr (RE = Tb, Dy, Ho, Er and Tm) with large magnetic moments and magnetic anisotropy energies using the PBE + U method. Our calculations indicate a half-metallic meta-stable state and a low-energy semi-conducting ground state in these 4f single-layers, which can be characterized by the location of the two-fold degenerate x(x2 – 3y2) orbital. The dynamical stability of single-layer REOBr is further confirmed using phonon dispersions. The predicted energy gaps ranging from 2.47 to 4.26 eV decrease with the atomic number of the rare-earth element. Meanwhile, very large spin moments and orbital moments up to 6.018 and 2.872 μB are found, which seem to be insensitive to the magnetic state. Furthermore, the magnetic anisotropy energies are evaluated and understood by a fourth-order non-uniaxial anisotropy mode. Diverse anisotropy energy landscapes including easy cone, easy plane, and easy axis are found, and an extremely high magnetic anisotropy energy of about 8 meV per RE atom is found in the single-layer DyOBr. Our investigations provide a unique insight into layered rare-earth magnetic materials and suggest the single-layer REOBr as competing candidates for low-dimensional data storage applications.

Wide-Range Frequency Control in Magnetoacoustic Resonator.

Acoustic resonators based on antiferromagnetic crystals of "easy plane" type, like α -Fe2O3 or FeBO3, are of interest for applications in magnetoacoustic sensors of electrical and mechanical values because of high sensitivity of their resonance frequency to variations of external magnetic field or mechanical stress. One of the requirements for magnetic control of resonators is a single-value dependence of resonance frequency on magnetic field strength. This requirement is violated when the geometry of resonator allows for crossover of acoustic modes in the range of magnetic field variation. Designing of resonators with frequency control in a wide range requires knowledge of field-dependent acoustic parameters of the crystals and appropriate method for calculation of the resonator eigenfrequencies. In this letter, we present the complete set of acoustic parameters deduced for α -Fe2O3 single crystal that are used for simulation of acoustic mode structures and spectra of vibrations in disk resonator. The results of simulation using COMSOL Multiphysics software are compared with experimental measurements carried out on two resonators of different ratios of sizes that illustrating continuous and discontinuous dependence of the resonance frequency on the magnetic field. Prevention of discontinuity by correction of the resonator geometry is demonstrated.

Probing the Axial Distortion Effect on the Magnetic Anisotropy of Octahedral Co(II) Complexes.

Three mononuclear octahedral Co(II) complexes are reported, [Co(py)4(SCN)2] (1), [Co(py)4(Cl)2]·H2O (2), and [Co(py)4(Br)2] (3), that exhibit different distortions with compression (1) or elongation (2 and 3) of the axial positions. Easy plane magnetic anisotropy was confirmed by magnetic, HF-EPR, and computational studies for all complexes. Further analyses indicate that both the sign and magnitude of zero-field splitting parameters experience a significant change (D ≥ ±150 cm-1) by tuning of the axial and equatorial ligand field strength. Slow magnetic relaxation is observed for all compounds which is dominated by the Raman process involving both acoustic and optical phonons.

Dislocation dissociation induces secondary twinning in titanium

The twin–twin interaction phenomenon in Ti is studied by incorporating experimental observation and theoretical analysis. Secondary $$ \{ {10\bar{1}2} \} $$ twins are stimulated in primary $$ \{ {11\bar{2}2} \} $$ and $$ \{ {11\bar{2}4} \} $$ via twinning dislocation dissociation. Primary twin variants are found either share the same $$ \langle {10\bar{1}0} \rangle $$ zone axis or with different zone axes. Schmid law, dislocation theory and crystallographic analysis are used to investigate the formation processes and physical mechanisms of the twin–twin interaction phenomenon. Results show that non-Schmid secondary twins are stimulated under the effect of primary twinning interactions. Besides to secondary twinning dislocations, glissile and sessile dislocations generate as a result of primary dislocation dissociation. Glissile dislocation glide on the easy slip prismatic plane, while sessile dislocation accumulates and leads to the increase of local strain.

Effect of the Crystallographic Texture Type on the Anisotropy of the Magnetic Leakage Field Parameters of Steel Sheets

This paper examines the distribution of the tangential and normal components of the magnetic leakage fields in pole-magnetized sheet materials, such as cold-worked structural steels St3, 09G2S, and 08G2B, as well as electrical steel with different grain structure and coarse-grained magnetically soft alloy Alfer, which have different types of texture induced by rolling and uniaxial tension. It has been found that even minor changes in the preferential orientation of easy magnetization axes 〈100〉 strongly affect the distribution of the tangential Нτ and normalHn components of magnetic leakage fields. For all studied materials, the magnitude ofНτ significantly exceeds that ofHn. However, in most cases, the componentНn exhibits a larger anisotropy thanНτ. Cold plastic working by rolling and uniaxial tension changes the texture state of the studied structural steels with the formation of multicomponent textures, which causes changes in the angular dependences of the parametersНτ and Hn. This fact indicates that the onset of plastic flow in a ferromagnetic material can be detected by changes in the form of circle diagrams of the leakage field components. The circle diagrams of the parametersНτ and Hn of deformed structural steels have the form of figure-eight patterns that are approximately perpendicular to each other. The position of the maxima of Нτ andHn on these diagrams corresponds to the position of the projections of the easy magnetization axes closest to the rolling plane, i.e., the directions along which iron and its alloys have the lowest strength. Therefore, it may be effective to estimate the anisotropy of strength properties of steel products with different texture states by the anisotropy of their magnetic parameters. More reliable results of magnetic texture analysis can be obtained by constructing full circle diagrams of the magnetic leakage field parameters.

Effect of interchain coupling in the frustrated spin one heisenberg model with easy plane single ion anisotropy

We study the quantum disordered phase of the anisotropic Heisenberg spin one model with ferromagnetic nearest-neighbor interactions, frustrating antiferromagnetic next-nearest-neighbor interactions along the chain and antiferromagnetic interchain couplings along the axes perpendicular to the chain. We use the SU(3) Schwinger boson technique and calculate the phase diagram at zero temperature. The gap as a function of temperature is also presented.

Nematic-Orbit Coupling and Nematic Density Waves in Spin-1 Condensates.

We propose the creation of artificial nematic-orbit coupling in spin-1 Bose-Einstein condensates, in analogy with spin-orbit coupling. Using a suitably designed microwave chip, the quadratic Zeeman shift, normally uniform in space, can be made to be spatiotemporally varying, leading to a coupling between spatial and nematic degrees of freedom. A phase diagram is explored where three quantum phases with the nematic order emerge: easy axis, easy plane with single-well structure, and easy plane with double-well structure in momentum space. By including spin-dependent and spin-independent interactions, we also obtain the low energy excitation spectra in these three phases. Last, we show that the nematic-orbit coupling leads to a periodic nematic density modulation in relation to the period λ_{T} of the cosinusoidal quadratic Zeeman term. Our results point to the rich possibilities for manipulation of tensorial degrees of freedom in ultracold gases without requiring Raman lasers, and therefore, obviating light-scattering induced heating.

Wave-transmitting material to optimize impedance matching and enhance microwave absorption properties of flaky carbonyl iron coating

Flaky carbonyl iron particles/nano silicon dioxide/Polyurethane (FCIP/SiO2/PU) composites coatings were fabricated. And FCIP were fabricated from sphere carbonyl iron particles (SCIP) by ball milling. The electromagnetic parameters of absorbers (SCIP, FCIP and SiO2) and the reflection loss (RL) of coatings were measured in the frequency range of 2–18 GHz. The results showed that the complex permeability and absorbing properties of FCIP are significantly enhanced compared with SCIP because of its smaller thickness and easy magnetization plane. In addition, as a low dielectric material, SiO2 can build more wave-transmission channels and optimize the impedance matching, making more electromagnetic wave transmitting into the coatings and being attenuated. Due to the addition of SiO2, the absorbing properties and effective absorption bandwidth of coatings are further enhanced. The reflection loss values exceeding − 10 dB can be obtained in the frequency range of 8.5–18 GHz with a thickness of 1 mm.

Efficacy of Erector Spinae Plane Block for Back Pain Referred from Visceral Pain in the Palliative Care Setting

Background: Erector spinae plane (ESP) block, an easy and safe interfascial plane block under ultrasound guidance, has an analgesic effect in various surgeries for chronic pain. However, no study has described the possible clinical efficacy of ESP block in palliative patients suffering from back pain referred from visceral pain. Case Report: Here we report three cases of successful ESP block at the middle to lower thoracic vertebras with 5–10 mL local anesthetic to relieve back pain referred from thoracic or abdominal visceral cancer pain. Back pain in these cases was derived from spinal extensor muscles supplied by the dorsal rami of the spinal nerve. Thoracic or abdominal visceral pain was suggested to stimulate the middle to lower thoracic dorsal rami of the spinal nerve. Conclusion: Despite the effect of ESP block on the ventral rami of the spinal nerve being uncertain, back pain accompanied by the lateral and medial branches of the dorsal rami of the spinal nerve, similar to that in these cases, can be relieved via ESP block. Therefore, ESP block can be easily and safely performed for relieving back pain referred from visceral pain in the palliative care setting. Further, to establish optimal volume, concentration of local anesthetic, and clinical efficacy, randomized control trials will be essential in the future. Key words: Erector spinae plane block, fascial plane block, referred pain, palliative care setting, dorsal rami of the spinal nerve, ventral rami of the spinal nerve, visceral pain, chronic pain

Magnetic field induced antiferromagnetic cone structure in multiferroic BiFeO3

Neutron diffraction measurements were performed under high magnetic fields up to 17 T in a multiferroic ${\mathrm{BiFeO}}_{3}$ single crystal, in which an intermediate magnetic (IM) phase has been found between the cycloid and canted antiferromagnetic phases [S. Kawachi et al., Phys. Rev. Mater. 1, 024408 (2017)]. We clearly found that the incommensurate magnetic peaks, which split perpendicular to the magnetic field in the cycloid phase, rotate by 90 deg to align parallel to the field in the IM phase. The magnetic structure in the IM phase can be best described by an antiferromagnetic cone (AF cone) structure. The transition from the cycloid to AF cone is of first order and the direction of the magnetic wave vector and the easy plane of the cycloidal component are rotated by 90 deg without changing the cycloidal modulation period, whereas the transition from the AF cone to canted antiferromagnetic phase is gradual and the cone angle becomes smaller gradually without changing the modulation period. Interestingly, the cycloidal component as well as the cone angle in the IM phase shows a large hysteresis between the field increasing and decreasing processes. This result, combined with the magnetostriction with a large hysteresis previously reported in the IM phase, suggests a strong magnetoelastic coupling.

Microscopic nature of drastic influence of hydrogen on the magnetic anisotropy of 5f -electron systems: The case of U2Ni2Sn

Recent experiments showed that hydrogenation of ${\mathrm{U}}_{2}{\mathrm{Ni}}_{2}\mathrm{Sn}$ leads to a dramatic change of the magnetic anisotropy (MA) from strongly uniaxial type to easy-plane type with easy axis and easy plane orthogonal to each other. We applied first-principles calculations aiming to understand the microscopic origin of the drastic MA change and distinguish between discontinuous and continuous scenarios of the transformation. The calculations combined with symmetry analysis revealed that the hydrogenation leads to the instability of both uniaxial and easy-plane states caused by the reduced symmetry of the atomic lattice. The obtained noncollinear noncoplanar magnetic states have the features of both apparently competing magnetic structures, which indicates the validity of the continuous scenario of the transformation. An insight into the active interatomic interactions shows that Dzyaloshinskii-Moriya interaction contributes to magnetic transformations and must be taken into account on the same footing as MA.

Ideal strengths and thermodynamic properties of W and W-Re alloys from first-principles calculation

Abstract First-principles calculation, quasi-harmonic approximation and thermal electronic excitation have been combined to examine ideal strengths and thermodynamic properties of W and W-Re alloys. It is found that the ideal tensile and shear strengths of W are decreased due to Re alloying, with the easy cleavage plane of both W and W-Re alloys found in (100) plane. Moreover, the derived temperature-dependent elastic properties explain the “Re softening effect”, and provide a deep understanding of the ductility of W-Re alloys as a function of the temperature. The results also reveal that Re alloying significantly increases the ductility of W, which is rare at low temperature in the temperature range 0−2000 K. The calculated results agree well with similar experimental observations in the literatures, and could explore their fundamental properties as well as various potential applications.

Magnetocrystalline Anisotropy and Spinorientation Phase Transitions of Co2z Hexaferrite Doped With Ti4+ and Zn2+ Ions

The paper presents the methodology for calculation of ferromagnetic resonance spectra of polycrystalline and powder hexaferrites with easy magnetization plane. Magnitudes of magnetocrystalline anisotropy fields and magnetomechanical ratios of the hexaferrites of Ba3Co1.5+хTiхFe24.5–2хO41 (0.0 ≤ х ≤ 1.0) and Ba3Co2.5–хZnxTi0.5Fe23O41 (0.0 ≤ х ≤ 1.2) (0.0 ≤ х ≤ 1.2) systems were determined from an experimental study of the parameters of ferromagnetic resonance at room temperature. The study of temperature dependences of initial magnetic permeability was used to determine the temperatures of spin-orientation phase transitions of these materials. It was shown that substitution of Co2+Ti4+ complex for Fe3+ ions leads to the widening of the temperature region of existence for the magnetic ordering of the easy magnetization plane type with high magnetic permeability in the microwave frequency region. Substitution of Zn2+ ions for some of the Co2+ ions increases the saturation magnetization.

Current-induced shuttlecock-like movement of non-axisymmetric chiral skyrmions

Current-induced motion of non-axisymmetric skyrmions within tilted ferromagnetic phases of polar helimagnets with the easy plane anisotropy is studied by micromagnetic simulations. Such non-axisymmetric skyrmions consist of a circular core and a crescent-shaped domain-wall region formed with respect to the tilted surrounding state. Current-driven motion of non-axisymmetric skyrmions exhibits two distinct time regimes: initially the skyrmions rotate towards the current flow direction and subsequently move along the current with the skyrmionic crescent first. According to the Thiele equation, the asymmetric distribution of the topological charge and the dissipative force tensor play an important role for giving the different velocities for the circular and the crescent-shaped constituent parts of the skyrmion what underlies such a shuttlecock-like movement. Moreover, the current-velocity relation depends on the angle of the tilted ferromagnetic phase what makes in particular the transverse velocity of skyrmions sensitive to their field-driven configurational transformation. We also argue the possibility of magnetic racetrack waveguides based on complex interplay of robust asymmetric skyrmions with multiple twisted edge states.

Magnetoelastic effects and random magnetic anisotropy in highly strained ultrathin Ni nanowires epitaxied in a SrTiO3 matrix

We analyze the magnetic anisotropy of Ni nanowires with diameters smaller than 5 nm. The nanowires are vertically epitaxied in a SrTiO3(001) matrix which generates huge tensile strains up to 3.6% along the nanowire axis. This leads to an unusual anisotropy, characterized by an easy magnetization plane perpendicular to the nanowire axis. Hysteresis cycles M(H) unveil an overall in-plane isotropy, while an opening of the M(H) cycles and thermal activation measurements indicate the presence of local energy barriers inside the nanowires. Surprisingly, the coercive field Hc(T) decays exponentially with increasing temperature, for both the easy plane and the hard axis. Based on these findings, we provide an analysis of magnetoelastic effects in the nanowires. By considering global averaging over the anisotropy distribution and local averaging according to the Random Magnetic Anisotropy model, we find that the global anisotropy, with its hard axis and isotropic easy plane, is related to the mean strain, while coercivity arises from local strain variations. We evidence that a thermally activated anisotropy softening occurs in the nanowires, in addition to Sharrock’s law of thermal reduction of coercivity. Possible mechanisms responsible for this thermal softening of anisotropy are proposed and discussed. Our study eventually allows to identify two major competing effects at play in the present system: an increasing magnetic anisotropy with increasing strain and a reduction of the anisotropy with increasing local strain fluctuations.