Ferromagnetic Behavior Research Articles

Antioxidant activity and cytotoxicity of greigite nanoparticles synthesized by hydrothermal technique.

The effects of 180, 210, and 230°C reaction temperatures on the structural and magnetic properties of synthesized iron sulfide nanoparticles were studied. The Rietveld refinement analysis result of the X-ray diffraction data indicated that greigite was the dominant phase in all samples. The sample was prepared at 210°C for 18h and had a greater wt% ratio of the greigite phase. The crystallite and particle sizes increased with increasing reaction temperatures. Scanning electron microscope images confirmed the presence of aggregation of synthesized rod-shaped nanoparticles. The magnetic hysteresis curves of all samples showed ferromagnetic behavior at room temperature. The magnetic saturation of three samples increases with increased reaction temperature, but the coercive force has the opposite behavior. Antioxidant activity and cytotoxicity of the sample synthesized at 210°C were investigated. This sample killed cancer cells at relatively moderate and high concentrations with high viability of normal cells, demonstrating the sample's suitability for use in killing cancer cells while avoiding normal cells.

Exploring the Mn doped BaTe alloy for spintronics and energy harvesting applications

In the present study, the ferromagnetic semiconductor behavior of Mn doped BaTe is reported along with their physical properties. The calculations are done by full potential linearized augmented plane wave (FP-LAPW) approach within spin-polarized density functional theory (SP-DFT). Formation energies were computed to satisfy the stability of reported alloys. The spin-polarization is included in the calculations to study the electronic (band structure (BS), density of states (DOS)) and magnetic characteristics. Ba1−xMnxTe elucidates the magnetic semiconductor nature with direct band gap (Eg) in both spin channels while indirect Eg (1.66 eV) is observed for pure BaTe compound. Stable ferromagnetic (FM) states are vindicated owing to the p-d hybridization which are contributors in inducing magnetic moments (μ B) at interstitial and non-magnetic sites. The optical parameters (reflectivity, absorption coefficient, refraction, optical conductivity and dielectric function) were computed within an energy range of 0–10 eV. Thermoelectric (TE) features are also figured using Boltaz-Trap code in terms of thermal and electrical conductivity, figure of merit, Seebeck coefficient and power factor. The analysis of optical parameters suggests that the considered alloys is active within visible to UV-range, having potential applications in optoelectronic, photovoltaic and thermoelectric applications.

Strain-induced giant enhancement and transformation of magnetocrystalline anisotropy in 1T-FeSe2 monolayer

Abstract The development of magnetic materials with large magnetic anisotropy energy (MAE) is crucial for magnetic storage and spintronics applications. The electronic structure and magnetic properties of 1T-FeSe2 monolayer have been systematically investigated by first-principles computational methods. The monolayer 1T-FeSe2 is confirmed to be a ferromagnetic semimetal with 100% spin polarization and exhibits pronounced magnetic anisotropy. It shows an easy magnetization plane in the two-dimensional plane and its MAE is as high as 8.13 meV. The MAE mainly originates from the contributions of transitions between Fe d_yz and d_(z^2 ), d_xyand d_(〖x^2-y〗^2 ) orbitals, while the contributions of transitions between px and py, px and pz orbitals of Se are also obvious. The biaxial strain significantly regulates the magnetic properties and electronic structures of the 1T-FeSe2 monolayer. Interestingly, the MAE increases significantly to 77.68 meV when the tensile strain increases to 3.5%, we can expect to achieve a reasonable value of MAE up to 98.95 meV by applying 5% tensile strain. In addition, the easy magnetization plane changes to perpendicular easy magnetization axis direction at -6% compressive strain or 7% tensile strain, which leads to a significant change in the band structure near the Fermi level. The 100% spin-polarized ferromagnetic semi-metallic behavior and the huge strain-induced magnetic anisotropy make the 1T-FeSe2 monolayer material promising for spintronics and magnetic data storage.

Unlocking antimicrobial activity of gamma irradiated iron-zinc nanoparticles

Water and foodborne diseases are generated by spoilage microorganisms with severe consequences on public health. Therefore, it is imperative to develop a way forward for their growth inhibition. In this contribution, iron-zinc (Fe-Zn) nanoparticles (NPs) were induced by gamma radiolysis, as potential antimicrobial agents. X-ray diffraction (XRD) showed the formation of cubic iron oxide and hexagonal zinc oxide as mixed phases in accordance with microscopic observations. Energy dispersive X-ray spectroscopy (EDS) depicted the presence of Fe, Zn, and O within the sample. Photoluminescence (PL) in line with vibrating sample magnetometer (VSM), confirmed the presence of oxygen vacancies with a ferromagnetic behavior. Besides, the antimicrobial activity was more pronounced against Dekkera bruxellensis.

Structural, Optical, and Magnetic Properties of Mn Doped Zn3P2 Diluted Magnetic Semiconductor Nanoparticles

Mn-doped Zn3P2-diluted magnetic semiconducting nanoparticles (Zn0.98Mn0.02P2, Zn0.96Mn0.04P2, Zn0.94Mn0.06P2, and Zn0.92Mn0.08P2) were synthesized by a conventional solid-state reaction followed by a subsequent vacuum annealing process. The formation of a tetragonal structure of pure and Mn-doped Zn3P2 was confirmed by X-ray diffraction studies, with no evidence of any further phases. Lattice parameters dicrease from a = b = 8.133 Å, c = 11.459 Å to a = b = 8.041 Å, c = 11.410 Å with increasing dopant concentration. Scanning electron microscpy analysis indicated that all samples that underwent doping exhibited agglomeration in the scanned range of 500 nm. Energy-dispersive X-ray analysis confirmed the presence of Zn, P, and Mn in the samples, and all of the synthesized samples achieved a nearly atomic ratio. In the diffused reflectance spectra, the optical band gap increases from 1.398 to 1.418 eV with increasing dopant concentration. PL has provided evidence indicating that the emission intensity of all doped samples remains constant with increasing dopant content from x = 0.02 to 0.08, with different excitation wavelengths (215 and 290 nm). Vibrating sample magnetometer tests confirmed the presence of ferromagnetic behavior at room temperature, and a positive correlation between saturation magnetization and Mn content, with the magnetic moment increasing from 0.0640 to 0.1181 emu g−1 with an increase in dopant content.

Effect of grain size on the dielectric and magnetic properties of YFeO3 ceramics densified by microwave sintering and spark plasma sintering from powders synthesized via reverse chemical co-precipitation

YFeO3 (YFO) ceramics were synthesized by reverse co-precipitation at different pH values followed by microwave sintering (MS) and spark plasma sintering (SPS) techniques. Also, the effect of the grain size on the magnetic and dielectric properties of the sintered ceramics was examined using various characterization methods. Moreover, FESEM micrographs showed that the particle size of the calcined samples has declined by increasing the pH value. Furthermore, the magnetization curves exhibited weak ferromagnetic behavior in the pre-sintered powder samples. Besides, the Ms value was enhanced from 1.26emu/g to 2.3emu/g by an increase in pH from 8.5 to 10.5 owing to reducing the particle size and subsequently raising the amount of uncompensated surface spins. Furthermore, the powder samples showed an increase in the Hc and Mr values from 15Oe to 28Oe and 0.127emu/g to 0.296emu/g, respectively, with a reduction in particle size from 0.632μm to 0.272μm. Additionally, the specimens processed through the sintering techniques demonstrated a remarkable reduction in magnetic characteristics. Therefore, a decrease in magnetic saturation values from 2.3emu/g to 0.43emu/g for the MS sample and to 0.17emu/g for the SPS specimen was attributed to a marked reduction in the amount of free surfaces and subsequently uncompensated surface spins. At last, the observed dielectric characteristics of all the sintered pellets had a common dielectric behavior. This signifies that by increasing the frequency the and tanδ decline at lower frequencies and become frequency-independent at higher frequencies based upon the Maxwell-Wagner polarization theory. On the other hand, the value for the SPS sample produced at pH=10.5 underwent a decline of 2.5 times at the low frequency of 200Hz compared to the MS one due to the significant decrement of the grain boundaries on account of the coarsening of grains.

Stabilization of various structural phases and magnetic properties of chemically synthesized Co-Ni-Ga nanoparticles

Polycrystalline Co-Ni-Ga ferromagnetic shape memory alloy nanoparticles with phase single austenite (A), martensite (M) and gamma (γ) structures have been obtained for the first time through a facile template-less chemical method. Average crystallite size of A, M and γ phase nanoparticles are 25 nm, 22 nm and 21 nm, respectively. All the synthesized nanoparticles exhibit soft ferromagnetic behavior with saturation magnetization varying from 21.22 to 77.65 emu/g and effective magnetic anisotropy of ∼105 J/m3 at 5 K. Ab initio studies have been performed to evaluate the magnetic moments of single A, M and γ phase. All the single phase nanoparticles have been ascertained to be in single-domain regime by estimating the single-domain size limit. This work showcases a simple methodology to prepare pure crystal phases in these nanoparticles. It also provides insight on the role of elemental precursors and processing conditions in designing Co-Ni-Ga nanoparticles for ferromagnetic shape memory applications.

Ferromagnetism behavior of Ni-doped Fe3O4 thin films synthesized by the SILAR technique

In this article, Ni-doped Fe3O4 thin films were synthesized by using the SILAR technique. The films were characterized through X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Raman, Photoluminescence and UV–Vis analysis. The XRD spectrum confirms the spinal structure of undoped and Ni-doped Fe3O4 thin films. The FESEM images show that Ni-doping has changed the morphology of thin films from a granular to a Spiky structure. The EDAX and XPS spectra show Fe, Ni and O elements are present in 1%Ni-doped Fe3O4 thin film. The vibrating sample magnetometer (VSM) studies showed ferromagnetism in undoped and Ni-doped Fe3O4 thin films. The ferromagnetism behavior of Ni-doped Fe3O4 thin films increases with the increase in Ni ion concentration.

Effect of rare earth (Sm3+) substitution in mixed Ni-Zn-Co ferrites: Structural, magnetic, and DC electrical resistivity studies

NiZnCo ferrite has good magnetic properties and is one of the core materials used in magnetic devices. The solid-state reaction approach is utilized to synthesize Ni0.4Zn0.35Co0.25Fe2-xSmxO4 (x = 0.0, 0.02, 0.04, 0.06, 0.08, and 0.1) ferrites for investigation of structural, morphological, functional, magnetic and electrical resistivity properties using various characterization techniques. The techniques used for characterization were XRD, SEM, FTIR, VSM, and DC electrical resistivity. XRD spectra were used to determine phase confirmation, cubic crystallite size, andtheir variation with dopant content. No additional phase or impurity was found. The SEM pictures revealed ahomogeneous spherical particle formation with minimal porosity. With absorption bands under 1000 cm−1, FTIR spectra indicate the formation of a spinel structure. Tetrahedral (580 to 599 cm−1) and octahedral (388 to 399 cm−1) bond changes can be seen in infrared spectra. The magnetic hysteresis curves revealed soft ferromagnetic behavior, with coercivity (Oe) (532.13 to 312.10Oe) rising and saturation magnetization (Ms) (83.51 to 60.75 emu/g) falling as doping concentration increased. The DC electrical resistivity of synthesized nanoparticles with various compositions was measured against higher temperatures to confirm their semiconductor nature. The findings demonstrated the typical decreasing trend with rising temperature.

Spin Seebeck effect and large spin conversion in amorphous Fe2TiSb/polycrystalline Y3Fe5O12 thin films

This study investigates spin current generation in a Fe2TiSb/Y3Fe5O12 multi-layer thin film as prepared via the magnetron sputtering method. Comprehensive characterization techniques are employed to assess film properties, including X-ray diffraction, energy-dispersive X-ray spectroscopy, Scanning electron microscopy, and Vibrating sample magnetometer. The Y3Fe5O12 material exhibits a polycrystalline ferromagnetic insulator behavior, while the 20 nm-thick Fe2TiSb film displays small ferromagnetic metal properties with an amorphous structure. Spin current analysis utilizes the longitudinal spin Seebeck effect configuration, considering magnetic field and temperature dependencies and the results show that spin conversion within the Fe2TiSb/Y3Fe5O12 structure is influenced by both the spin Seebeck effect and the anomalous Nernst effect, resulting in an overall spin signal enhancement. The spin Seebeck coefficient of Fe2TiSb/Y3Fe5O12 was approximately 0.103 μV/K within a magnetic field of 300 mT.

First principle investigation of half metallic ferromagnetism and thermoelectric behavior of MgSm2(S/Se)4 spinels for spintronic and energy harvesting applications

Density functional theory investigates the spin-dependent structural, electronic, magnetic, and thermoelectric properties of MgSm2 × 4 (X = S, Se). The optimization uses PBEsol-GGA to compute the lattice constant, bulk modulus, and energies. The Heisenberg model has been applied to calculate the Curie temperature which shows ferromagnetism above room temperature. The negative values of formation energy confirm their thermodynamic stability. The half-metallic ferromagnetism (HMF) is observed from the metallic character in the spin-up channel and insulating behaviour in the spin-down channel. The density of states plots indicates that 4f-states of Sm, 3s states of Mg and 3p/4p states of S/Se play a crucial role in forming band edges. The computation of exchange energies and exchange magnetic constants has assisted in determining these spinels' ferromagnetic and 100 % spin polarized nature. The magnetic moments (MM) arise from the p-f hybridization of Sm and X atoms. The robust half-metallicity and high Curie temperature make the studied materials suitable for spintronic applications. In addition, calculating temperature dependent thermoelectric parameters reveals an extra degree of applications of these materials for thermoelectric devices.

Design of 2D half-metallic [formula omitted] with robust ferromagnetism and high Curie temperature

Two-dimensional 2D ferromagnetic materials featuring intrinsic half-metallicity (HM) and high critical temperature Tc emerge as promising candidates for innovative low-dimensional spintronic devices. In this study, we employ first-principles calculations to predict a novel 2D half-metallic ferromagnet CoAl2S4 monolayer, a member of the layered AB2X4 family. The material’s energetic, mechanical, and dynamical stability is affirmed through analyses of its cohesive energy, elastic constants, and phonon spectrum, respectively. The ferromagnetic behavior observed in CoAl2S4 can be explained by the superexchange interaction of Co-S-Co bonds, consistent with the Goodenough–Kanamori rules. Notably, CoAl2S4 displays robust ferromagnetism with a Curie temperature reaching up to 435 K. The band structures show a large half-metal gap (2.83eV), ensuring the stability of the half-metallic state. Additionally, the CoAl2S4 monolayer demonstrates a preferential easy magnetization along the out-of-plane direction. Consequently, the rich CoAl2S4 monolayer is expected to boost advancements in spintronics, magnetostrictive materials, and magnetic memory devices.

Facile synthesis of co-axially electrospun Co-C nanofibers and their ferromagnetic behavior

We describe a simple co-axial electrospinning approach followed by a carbonisation process to create cobalt-carbon (Co-C) nanofibers that are then thoroughly analysed using various techniques. X-ray diffraction measurements showed the creation of pure crystalline cobalt with face-centered cubic (fcc) structure, and average crystallite size was determined using the Debye–Scherrer formula. The average crystallite size has been calculated to be in the range of 10 − 15 nm. According to the Raman investigation, all Co-C nanofibers have an amorphous carbon structure with little graphitic behaviour. Field emission scanning electron microscopy was used to determine the shape and average diameter of electrospun nanofibers. The field-dependent magnetic characterisation demonstrated a satisfactory ferromagnetic behaviour with maximum saturation magnetisation values of 10, 10.2, and 11.2 emu/g for Co12.5-C sample at 300, 100, and 5 K, respectively. Compared to bulk cobalt, the produced Co-C nanofibers have a high coercivity value. With average crystallite size, the coercivity varies. Again, magnetisation versus temperature measurements have supported the existence of ferromagnetism because there is no evidence of blocking temperature or any transitional behaviour below 300 K. As a result, applications for microwave absorption, catalysis, and several magnetic recording devices can benefit from the coupling of ferromagnetic properties with carbon nanofiber materials.

Epitaxial growth and magnetic properties of Mn5(SixGe1-x)3 thin films

Structural and magnetic properties of Mn5(SixGe1-x)3 thin films were investigated. Ferromagnetic Mn5Ge3 and anti-ferromagnetic Mn5Si3 thin films have been synthesized and characterized as these compounds exhibit interesting features for the development of spintronics. Here, Mn5(SixGe1-x)3 thin films were grown on Ge(111) substrates by co-deposition using molecular beam epitaxy. Crystalline thin films can be produced with controlled Si concentrations ranging from 0 to 1. The thin films were relaxed by dislocations at the interface with the substrate. A lattice parameter variation was observed as the Si content increased, which is comparable to previous works done in bulk. Reflection high-energy electron diffraction diagrams and X-ray diffraction profiles showed that lattice parameters a and c are shrinking and that the surface roughness and crystallinity degrade as the Si amount increases. Magnetometric measurements revealed a ferromagnetic behavior for all Si concentrations. The measured average ferromagnetic moment per manganese atom decreased from 2.33 to 0.05 μB/Mn atom. No ferro to anti-ferromagnetic transition was observed contrary to the bulk Mn5(SixGe1-x)3 compound.

Facile synthesis of Mn doped ZnO for the sensing of ammonia

The variation of possessions of Mn doped in ZnO thin films grown by SILAR technique for various Mn concentrations presented. Thin films of Mn doped ZnP were deposited and uniformly annealed at 300 °C for a 30 min. The annealed films are then characterized by various methods like XRD, SEM, EDAX, VSM respectively. The x-ray diffraction studies confirm the emergence of ZnO. From the SEM, various morphologies were identified based on concentration of the solution bath employed. Due to this reason, spherical shoot, rice and flower morphologies were observed on the surface of the films. These morphologies may influence the application of ammonia gas sensor. From compositional analysis (EDAX), the presence of dopant and the variation in composition of doped materials were estimated. Magnetic studies shows, these films show ferromagnetic behaviour at room temperature. The ammonia gas response of the Mn doped ZnO thin films varied with Mn concentration of 0, 5 and 10. The outcomes of the gas sensing experiments showed that the Mn doped ZnO thin film was more sensitive to ammonia, but that sensitivity decreased as gas pressure increased. Ammonia gas showed an increase in the acidic surface properties of Mn-doped ZnO thin film. At room temperature, Mn-doped ZnO (0 %, 5 % and 10 %) showed responses of 19.20, 27.61 and 32.26 to 100 ppm NH3 gas, which were significantly higher than those of ZnO. The Mn-doped ZnO sensor shows excellent selectivity compared to ZnO and has good stability.

Electronic structure of double perovskite SrTi0.5Co0.5O3: order, disorder, and vacancy effects

In this study, we investigate the electronic structure of the ordered/disordered double perovskite SrTi0.5Co0.5O3 (STCO) using density functional theory (DFT) and the full-potential linearized augmented plane wave method. Detailed structural and magnetic stability analysis revealed that Sr2TiCoO6 crystallizes in the tetragonal I4/m space group, in which Co4+ and Ti4+ ions are distributed in an alternating arrangement along three directions. Notably, Sr2TiCoO6 exhibits a half-metallic property and exhibits ferromagnetic (FM) behavior, originating from the Co4+-O2--Ti4+ bonds and the high spin state of cobalt. Additionally, a chemical/magnetic stability analysis was carried out to identify the ground state structure in disordered STCO. The investigation identified a two-dimensional-like configuration (referred to as STC5FM) characterized by ferromagnetic order. This particular arrangement represents the most chemically stable layered configuration, featuring a maximal occurrence of Co–O–Co chains. Thus, Co4+ ions exhibit an intermediate spin state following Goodenough-Kanamori-Anderson rules of ferromagnetic mechanism. Interestingly, this structure also displays ferromagnetism at room temperature, accompanying with semiconductor properties. The study also explored the impact of oxygen vacancies. Remarkably, the ferromagnetic attributes remain robust even in the presence of oxygen vacancies. Moreover, a transition from semiconductor to metal behavior becomes evident under these conditions.

Comparison of the Magnetic and Structural Properties of MnFePSi Microwires and MnFePSi Bulk Alloy.

We provide comparative studies of the structural, morphological, microstructural, and magnetic properties of MnFePSi-glass-coated microwires (MnFePSi-GCMWs) and bulk MnFePSi at different temperatures and magnetic fields. The structure of MnFePSi GCMWs prepared by the Taylor-Ulitovsky method consists of the main Fe2P phase and secondary impurities phases of Mn5Si3 and Fe3Si, as confirmed by XRD analysis. Additionally, a notable reduction in the average grain size from 24 µm for the bulk sample to 36 nm for the glass-coated microwire sample is observed. The analysis of magnetic properties of MnFePSi-glass-coated microwires shows different magnetic behavior as compared to the bulk MnFePSi. High coercivity (450 Oe) and remanence (0.32) are observed for MnFePSi-GCMWs compared to low coercivity and remanent magnetization observed for bulk MnFePSi alloy. In addition, large irreversibility at low temperatures is observed in the thermal dependence of magnetization of microwires. Meanwhile, the bulk sample shows regular ferromagnetic behavior, where the field cooling and field heating magnetic curves show a monotonic increase by decreasing the temperature. The notable separation between field cooling and field heating curves of MnFePSi-GCMWs is seen for the applied field at 1 kOe. Also, the M/M5K vs. T for MNFePSi-GCMWs shows a notable sensitivity at a low magnetic field compared to a very noisy magnetic signal for bulk alloy. The common features for both MnFePSi samples are high Curie temperatures above 400 K. From the experimental results, we can deduce the substantial effect of drawing and quenching involved in the preparation of glass-coated MnFePSi microwires in modification of the microstructure and magnetic properties as compared to the same bulk alloy. The provided studies prove the suitability of the Taylor-Ulitovsky method for the preparation of MnFePSi-glass-coated microwires.

DFT+U, TB-mBJ, and hybrid approaches: investigating electronic topology and magnetic properties in Sn-doped Co2TiGa

Cobalt-based Heusler compounds represent a new class of Heusler alloys which absorbed a lot of attention due to their performance in spintronics and magnetic devices. in this paper we have studied and analyzed the electronic structure and half-metallic ferromagnetic properties of Co2TiGa and Sn substituted at Ga site via the density functional theory (DFT) based first principle calculations with GGA-PBE, PBE+U, TB-MBJ exchange correlation potential and HSE06 approach. The band structure topology indicates that the parent ternary Heusler compound is ferromagnetic half-metallic with a half-metallic gap (band gap in the minority channel). The gap is increased according to the correction made on the exchange correlation potential. The half-metallic ferromagnetic behavior is confirmed by the total magnetizations which are very close to integrals Bohr magneton (1 μ B and 3μ B for Co2TiGa and Mn2TiGa0.5Sn0.5, respectively). The origin of half-metallic ferromagnetic is the p − d exchange and double-exchange interaction between the Co d-t2g states and neighboring Ti atom. The substitution effect on half-metallicity for Co2TiGa0.5 Sn0.5 was investigated in the tetragonal structure. The spontaneous magnetization obeyed the Slater-Pauling rule, indicating the Co2TiGa0.5 Sn0.5 is half-metal with 100% spin polarization.

New in situ generated acylhydrazidate-coordinated complexes: Syntheses, structural characterizations and magnetic properties

The present study reports the successful synthesis of three new magnetic coordination polymers, namely [Mn(BPTH)(H2O)]n (1), [Co(BPTH)(phen)]n (2), and [Co(BPTA)(phen)(H2O)2]n (3), through a solvothermal method (H2BPTH = biphenyl-3,3′,4,4′-tetracarboxyhydrazide, H2BPTA = biphenyl-3,3′,4,4′-tetracarboxylic acid, phen = 1,10-phenanthroline). In compounds 1 and 2, the bishydrazide ligand H2BPTH is formed by in situ acylation of H2BPTA with hydrazine hydrate. All the three title compounds contain M2O2 clusters (M=Mn(1), Co(2) and Co(3)). In compound 1, the amido-oxygen atoms O1 coordinate with Mn2+ to form a Mn2O2 cluster, while the adjacent Mn2O2 cluster is interconnected by the ligand's oxygen atoms O3 and O4, resulting in an infinite expansion into a 3D network structure. Compound 2 exhibits a 1D chain structure containing Co2O2 clusters, which further extends into a 2D supramolecular layer through π···π stacking interactions. Compound 3 comprises adjacent Co2O2 clusters interconnected by oxygen atoms O1, O2, and O5 on the ligand to form a 2D layered architecture. The 2D layers are linked through intermolecular O–H···O hydrogen bonds of H2BPTA ligands to form a 3D supramolecular network. Magnetic measurements reveal weak ferromagnetic behavior for compound 1 while compounds 2 and 3 exhibit weak antiferromagnetic interactions at different temperatures. Overall, this research presents new insights into the design and synthesis of coordination polymers with diverse structures and magnetic properties.

RKKY interaction in helical higher-order topological insulators

Abstract We theoretically investigate the RKKY interaction in helical higher-order topological insulators (HOTIs), revealing distinct behaviors mediated by hinge and Dirac-type bulk carriers. Our findings show that hinge-mediated interactions consist of Heisenberg, Ising, and Dzyaloshinskii-Moriya (DM) terms, exhibiting a decay with impurity spacing $z$ and oscillations with Fermi energy $\varepsilon_F$. These interactions demonstrate ferromagnetic behaviors for the Heisenberg and Ising terms and alternating behavior for the DM term. In contrast, bulk-mediated interactions include Heisenberg, twisted Ising, and DM terms, with a conventional cubic oscillating decay. This study highlights the nuanced interplay between hinge and bulk RKKY interactions in HOTIs, offering insights into the design of next-generation quantum devices based on the HOTIs.