Variation Of Magnetic Moment Research Articles

The adsorption characteristic of As2, As2O3, Pb, PbO on double transition-metal pyridine-tetranitrogen-annulene membrane

The arsenic and lead compounds produced by coal combustion have serious impacts on human health and the environment, making it urgent to simultaneously remove arsenic and lead. In this work, the adsorption characteristics of As2, As2O3, Pb and PbO on 2D Double Transition-Metal Pyridine-Tetranitrogen-Annulene membrane (DTM-PTA, TM=Co, Cu, Zn) are investigated through density functional theory calculations. The adsorption energy, bonding mechanism, electronic and magnetic properties are analyzed in detailed. Firstly, the distribution density of transition metal atoms as adsorption active sites is high, which is conducive to the adsorption of molecules. The results demonstrate that the DCo-PTA is a promising adsorbent for simultaneously removing As2, As2O3, Pb and PbO with highest adsorption energy. According to the variation of magnetic moment, DCu-PTA and DZn-PTA can detect the adsorption of PbO in the mixture of As2, As2O3, Pb and PbO. In addition, the adsorbed molecules can regulate the array of spin electron. Although temperature hinders the adsorption process of molecules, DCo-PTA can still spontaneously adsorb these molecules within the temperature range of 300–1000 K. This indicates that DCo-PTA is an excellent adsorbent which can work in high temperature.

Strain-insensitive ferromagnetic SrRuO3 thin films with ferrimagnetic CoFe2O4 buffer layer

Flexible electronics, such as wearable devices and biosensors, require materials that maintain their properties under mechanical stress. A recent study addresses this by focusing on SrRuO3 (SRO) thin films, which typically suffer reduced coercivity under strain. Herein, we introduce a novel approach by using CoFe2O4 (CFO) as a buffer layer in SRO/CFO/F-mica heterostructures to address this issue. When subjected to a strain of up to ±0.553 %, these heterostructures displayed a mere 11 % variation in saturation magnetic moment and coercive field, significantly outperforming SRO/BaTiO3 configurations, which showed a 95 % reduction in coercivity at only −0.3 % strain. This result demonstrates the effectiveness of the CFO layer in stabilizing the magnetic properties of SRO films against external mechanical deformations. These findings mark a significant advancement in the development of mechanically robust thin films for complex oxide heterostructures in flexible device applications.

Research on the de-tumbling method of magnetic moment variation of two stars based on the tangential formation

High-speed space debris threatens the safety of satellites in orbit, making the efficient removal of this debris an increasingly unavoidable necessity. By exploring the non-contact de-tumbling method for high-speed rotating targets, a de-tumbling technique is proposed. This method relies on leveraging the differential magnetic moments of two satellites arranged in tangential formation. Two single-coil electromagnetic satellites form a uniform magnetic field at the rotating targets, forming a tangential collinear distribution. The de-tumbling method of the simultaneous change of the magnetic moment of two satellites and the change of magnetic moment of one satellite and the other satellite is explored, and the de-tumbling effect is compared through numerical simulation. The simulation results indicate that the de-tumbling effect of the latter method is superior. Additionally, there is minimal variation observed in the relative distance between servicing stars and between servicing stars and target stars throughout the de-tumbling process.

Effect of codoping of rare earth elements and Cr on multiferroic, optical and photocatalytic properties of BiFeO3

In the present work, first principle calculations have been performed to study the combined effect of A (Bi) and B (Fe) site doping on the structural, multiferroic, optical and photocatalytic properties of BiFeO3 (BFO). Rare earth elements (La, Ce, Gd, Nd, Er and Eu) are doped at the A-site while Cr is doped at the B-site in perovskite BFO. A variation in total magnetic moments and spontaneous polarization of the doped systems is observed that are governed by the introduction of the rare earth elements. A maximum polarization of 110μC/cm2 is obtained for (Gd,Cr) doped BFO and the maximum magnetization of 5.1μB/cell is obtained for (Nd,Cr) doped BFO. From the study of partial electronic density of states it has been observed that amongst all the dopants incorporated as rare earth elements, the (Er,Cr)BFO system exhibits the minimum bandgap of 1.94 eV and thus shifts the absorption edge deep into the visible region which has been confirmed through the optical spectra. The band-edge alignment of the pure and codoped systems has revealed that (Er,Cr)BFO exhibits the maximum potential to be a promising photocatalyst with improved efficiency as compared to pristine BFO.

Unveiling the magnetic structure and phase transition of Cr2CoAl using neutron diffraction

We report the detailed analysis of temperature dependent neutron diffraction pattern of the Cr2CoAl inverse Heusler alloy and unveil the magnetic structure up to the phase transition as well as its fully compensated ferrimagnetic nature. The Rietveld refinement of the diffraction pattern using the space group I4¯m2 confirms the inverse tetragonal structure over the large temperature range from 100 to 900 K. The refinement of the magnetic phase considering the wave vector k= (0, 0, 0) reveals the ferrimagnetic nature of the sample below 730±5 K. This transition temperature is obtained from empirical power law fitting of the variation in the ordered net magnetic moment variation in intensity of (110) peak as a function of temperature. The spin configuration of the microscopic magnetic structure suggests the nearly fully compensated ferrimagnetic behavior where the magnetic moments of Cr2 are antiparallel with respect to the Cr1 and Co moments. Moreover, the observed anomaly in the thermal expansion and lattice parameters at 730±5 K suggests that the distortion in the crystal structure may play an important role in the magnetic phase transition.

First-principles calculations of the electronic, optical properties and quantum capacitance of Mn doped Sc2CO2 monolayer under biaxial strain

The electronic structures and quantum capacitance of Mn atom doped Sc2CO2 under biaxial strain are investigated by first-principles calculations. The results indicate that pristine Sc2CO2 monolayer is nonmagnetic, while Mn doping makes the system have the magnetic character, which is mainly from Mn and C atoms neighboring to Mn atom. The total magnetic moment under strain ranges from 2.16 μB to 2.69 μB. The local magnetic moment of Mn atom under strains ranges from 2.59 μB to 4.33 μB, and the variation in local magnetic moment has the largest value of 1.84 μB. Spin-up band structures under strain exhibit the characteristic of the indirect semiconductor, and have the largest band gap of 0.3 eV at −2 % strain. The spin-down band structures under strain show the character of direct semiconductor and the largest band gap is 1.83 eV at 2 % strain. Sc2CO2-Mn under strains except +5 % are suitable for cathode material, while Sc2CO2-Mn with +5 % strain changes to cathode material in ionic/organic system. Effective mass, work function, and optical properties are further explored.

Highly sensitive and selective sensing-performance of 2D Co-decorated phthalocyanine toward NH3, SO2, H2S and CO molecules

Developing excellent sensing-materials for detecting and monitoring toxic gases in the air is significant for environmental monitoring and industrial emission evaluation. Herein, the first-principles calculations were employed to systematically investigate the adsorption characteristics of twelve different gas molecules (NH3, NO, NO2, SO2, H2S, CO, CO2, CH4, H2O, H2, O2, N2) on the two-dimensional phthalocyanine (Pc) and Co decorated phthalocyanine (CoPc), the electronic properties of various adsorption systems and their sensing-mechanism were also elucidated. The results show that the toxic NH3, NO, NO2, SO2, H2S are chemically adsorbed on the pristine Pc surface, whereas the poor sensitivity of Pc monolayer makes it not suitable to be a sensing-material. By contrast, the CoPc monolayer exhibits the appropriate adsorption strength toward the six poisonous gases (NH3, NO, NO2, SO2, H2S, CO), which is detailedly explained by the analysis of charge transfer, charge density difference and density of states. Moreover, the CoPc monolayer possesses high selectivity to those six gases even if it is in a humid environment. The CoPc monolayer also has excellent sensitivity for those toxic gases due to the obvious variations of bandgap, magnetic moment or work function. Additionally, the recovery time of NH3, SO2, H2S and CO is estimated to be about 3.91 min, 0.02 s, 24.19 ns and 226.38 ns at room temperature, respectively. Consequently, the CoPc monolayer based gas sensor has a great potential application for the NH3, SO2, H2S and CO detection.

Key performance of tunneling magnetoresistance sensing unit modulated by exchange bias of free layer

Optimizing sample structural parameters, magnetic field annealing, series-parallel bridge design, current thermal effect, and additional bias magnetic field are common methods used for controlling the tunneling magnetoresistance (TMR) magnetic sensing performance. By employing these methods, key performance parameters of TMR sensors such as sensitivity, noise resistance index, linearity, and linear magnetic field range can be optimized and improved. Changing the sample structural parameters, such as the pinning layer, free layer, and barrier layer materials and thickness of the TMR magnetic sensing unit, can change the exchange bias field and thus enhance the TMR magnetic sensing performance parameters. In this study, through micromagnetic simulation and experimental measurements, it is discovered that by modifying the exchange coupling in the free layer CoFeB/Ru/NiFe/IrMn, the exchange bias field magnitude of the TMR free layer can be modulated, leading to improved performance of the TMR magnetic sensing unit. As the IrMn pinning effect is gradually enhanced, the linear magnetic field range of the TMR magnetic sensing unit increases, but the magnetic field sensitivity decreases. It is further found that the linearity of the TMR magnetic sensor is optimal within a range of ±0.5 times the magnetic moment variation of the free layer (primarily the CoFeB layer). Through our work, the effect of exchange bias field (caused by the pinning IrMn of the free layer) on the magnetic sensing performance is verified in the TMR magnetic sensing unit. Our work demonstrates more possibilities for designing and optimizing TMR magnetic sensors, enriching the dimensions of magnetic sensing performance modulation.

HYDROTHERMAL TEMPERATURE INFLUENCE ON MAGNETIC AND FMR PROPERTIES OF HEMATITE NANOPARTICLES

Investigation of the role of hydrothermal temperature on hematite nanoparticles structural, magnetic, and ferromagnetic resonance (FMR) properties was done. Ferric chloride and sodium hydroxide were used as the starting precursors. The hydrothermal temperature was varied in the range of 140–200∘C by a step of 20∘C. XRD, SEM, VSM, and FMR analyses were used to check the particles’ properties. The prevailing strongly phase was hematite with some small peaks related to other phases. A reduction in lattice constant and increase in the crystallite size to more than 27[Formula: see text]nm is observed. The particles’ morphology exhibited polygon particles down to spherical particles as the average particle size gets larger up to 45[Formula: see text]nm. The hysteresis loops showed unsaturated curves with rising coercivity up to 150Oe. The antiferromagnetism permeability, magnetization saturation, and dipole moment were found by Langevin fitting to the experimental hysteresis loops, where all of them have the same behavior represented by an initial drop followed by increase in their values. The FMR spectra are characterized by low intensities and low linewidths accompanied by very low blue shift in the resonance field. All samples showed Lorentzian distribution as checked by the Lorentz function. Landé [Formula: see text]-factor has values very close but less than 2 due to the effect of crystal field and particle magnetic moment variations.

Magnetoelastic anisotropy in Heusler-type Mn2−δCoGa1+δ films

Perpendicular magnetization is essential for high-density memory application using magnetic materials. High-spin polarization of conduction electrons is also required for realizing large electric signals from spin-dependent transport phenomena. Heusler alloy is a well-known material class showing the half-metallic electronic structure. However, its cubic lattice nature favors in-plane magnetization and thus minimizes the perpendicular magnetic anisotropy (PMA), in general. This study focuses on an inverse-type Heusler alloy, Mn$_{2-\delta}$CoGa$_{1+\delta}$ (MCG) with a small off-stoichiometry ($\delta$) , which is expected to be a half-metallic material. We observed relatively large uniaxial magnetocrystalline anisotropy constant ($K_\mathrm{u}$) of the order of 10$^5$ J/m$^3$ at room temperature in MCG films with a small tetragonal distortion of a few percent. A positive correlation was confirmed between the $c/a$ ratio of lattice constants and $K_\mathrm{u}$. Imaging of magnetic domains using Kerr microscopy clearly demonstrated a change in the domain patterns along with $K_\mathrm{u}$. X-ray magnetic circular dichroism (XMCD) was employed using synchrotron radiation soft x-ray beam to get insight into the origin for PMA. Negligible angular variation of orbital magnetic moment ($\Delta m_\mathrm{orb}$) evaluated using the XMCD spectra suggested a minor role of the so-called Bruno's term to $K_\mathrm{u}$. Our first principles calculation reasonably explained the small $\Delta m_\mathrm{orb}$ and the positive correlation between the $c/a$ ratio and $K_\mathrm{u}$. The origin of the magnetocrystalline anisotropy was discussed based on the second-order perturbation theory in terms of the spin--orbit coupling, claiming that the mixing of the occupied $\uparrow$- and the unoccupied $\downarrow$-spin states is responsible for the PMA of the MCG films.

Origin of magnetic field-induced magnetic anisotropy in amorphous CoFeB thin films

Magnetic anisotropy (MA) is an important property of magnetic materials, which not only determines the orientation of the magnetic moment in the magnetic material but also influences the working frequency of magnetoelectric devices. Unrevealing the origin of MA has become an important topic and attracts lasting interest. Here, we report a quite significant magnetic field-induced uniaxial MA in amorphous CoFeB thin films containing double ferromagnetic atoms. The thickness independence of MA was obtained by observing a series of hysteresis loops and magnetic domains. The MA is proved subtly to be related to the variation of orbital magnetic moment acquired by ferromagnetic resonance. Furthermore, we found that atoms combine into clusters and incline to an order in amorphous CoFeB thin films with field-induced MA. Based on these experimental results, we proposed a direction-like order model to interpret the origin of magnetic field-induced MA in amorphous CoFeB thin films well.

Mechanism of strain-induced magnetic properties changes for metal magnetic memory technology on atomic scale

Magnetic non-destructive testing technology is widely used to detect stresses and defects in ferromagnetic materials based on the magneto-mechanical coupling effect. In the existing studies, calculated are the magnetic moment variations of the <i>α</i>-Fe system under axial tension and compression by using first-principles study, and the magneto-mechanical coupling mechanism is preliminarily discussed at an atomic level for the magnetic testing technology. In this work, taking the more complex doping systems Fe-C and Fe-Mn for examples, under different loading conditions of tension, compression and shearing, the coupling mechanisms such as the magnetic moment changes in different types of atomic doping systems are discussed in detail. The results show that the <i>α</i>-Fe and doping systems follow different changing laws of magnetic moments and energy under different types of strains. The detailed analyses of the density of states, the band structure, and the atomic magnetic moment show that doping elements change the morphology of band structure and the peak value of density of states by affecting the magnetic moment of Fe atoms, which leads the changing laws of magnetic moment and energy to be different from each other. In this work, discussed are the magneto-mechanical effects on the atomic level for ferromagnetic materials with different loading types, different doping elements and different element content. The results can be used as an important part of the multi-field coupling mechanism for magnetic testing technology.

RETRACTED: An Ab initio study on effects of doping into Pt13 cluster with Ag, Ir and Pd

It is well known that doping is an efficient tool to modify the properties of clusters. Here, the results of the ab initio calculations on the effects of substitutional doping of Ag, Ir, and Pd atoms on the atomic and electronic structure of Pt 13 cluster are reported. The plane wave method and spin-polarized Exchange-correlation function have been used to study the various low-lying isomers of Pt 13 and to identify the lowest energy structures of the doped clusters. Moreover, this work involves studying about different doping sites and different magnetization values, exclusively for each isomer. Doing this way, the stability of the atom cluster has been analyzed and that is based on the low energy of the isomers calculated by the total energy with spin-polarized, lowest values of HOMO-LUMO gap, and higher values of the binding energy of each atom in the Pt 13 cluster structure. The resulting lowest energy structures show that in the case of Pt 12 Ir, the lowest energy isomer changes compared to the Pt 12 Ag and Pt 12 Pd clusters. Further, Bader charge analysis has been performed for calculating the charge transfer between the dopant and the host cluster which shows a charge transfer from −1.37 to +0.74 e. The study also reports about the changes that had happened in the electronic structure and magnetic properties of the Pt 13 cluster due to the dopant. This work helps to understand about the energy changes that occur during magnetic moment variations on the atomic cluster, DoS, and about analyzing this energy changes while spinning the atoms. • Effects of substitutional doping of Ag, Ir and Pd atoms with atomic structure of Pt13 cluster. • Study on several low-lying isomers of Pt13 cluster to identify the lowest energy structures of the doped clusters using Exchange-correlation functional methods. • Changes in energy by varying the magnetic moments on the cluster in order to obtain the lowest energy spin isomer. • Usage of Double Triangle, a distorted CDT, FCC-1, Double pyramid, Icosahedron and Decahedron. Total energy calculation on Vertex, Capping and Center doping sites on each isomer.

First principles and atomistic calculation of the magnetic anisotropy of Y2Fe14B

We present a study of the effects of strain on the magnetocrystalline anisotropy energy and magnetic moments of Y2Fe14B bulk alloy. The study has been performed within the framework of density functional theory in its fully relativistic form under the generalized gradient approximation. We have studied seven different in-plane a lattice constant values ranging from 8.48 up to 9.08 Å with an increment of δa=0.1 Å. For each a value, we carried out an out-of-plane c parameter optimization, achieving the corresponding optimized lattice pair (a,c). We find a large variation in the site resolved magnetic moments for inequivalent Fe, Y, and B atoms for different lattice expansions and a negative contribution to the total moment from the Y sites. We find a strong variation in the magnetocrystalline anisotropy with the c/a ratio. However, the calculated variation when coupled with thermodynamic spin fluctuations is unable to explain the experimentally observed increase in the total magnetic anisotropy, suggesting that a different physical mechanism is likely to be responsible in contrast with previous interpretations. We show that opposing single- and two-ion anisotropy terms in the Hamiltonian gives good agreement with the experiment and is the probable origin of the non-monotonic temperature dependence of the net anisotropy of Y2Fe14B bulk alloy.

Nanoporous Pd1−xCox for hydrogen-intercalation magneto-ionics

The use of hydrogen atoms for magneto-ionic applications has only been explored recently. Benefits of hydrogen compared to other ionic species for tuning magnetism are high switching speed and large changes in magnetic moment. Here, we test the influence of hydrogen intercalation on magnetism in nanoporous Pd(1−x)Cox, with Co being located in superparamagnetic clusters, building upon a previously suggested material system. Tailoring the Co concentration and distribution allows the magnitude of the magneto-electric effect to be influenced as well as to gain a deeper understanding of the interaction of hydrogen with magnetic clusters. In situ magnetization measurements are conducted to directly observe the variation in magnetic moment upon hydrogen-charging in nanoporous Pd(1−x)Cox. Temperature-dependent magnetization curves show that interstitial hydrogen atoms lead to an increase in magnetic anisotropy energy, a coupling of individual Co-rich clusters, and the concomitant blocking of their magnetic moments. The large obtained magnetic switching effects upon hydrogen-charging at room temperature (αC,V > 400 Oe V−1; ΔM = 1.5 emu g−1) open up new possibilities to use magneto-ionic effects for real-life applications in magnetic devices.

Electronic structure, magnetic properties and martensitic transformation of Ga2MnTM (TM = Sc, Y, Lu) Heusler alloys

The atomic site occupation, electronic structure, magnetism, martensitic transformation of Ga2-based Heusler alloys Ga2MnTM (TM = Sc, Y, Lu) have been investigated by first-principles calculations. For three alloys in cubic phase, the L21-type structure is more stable than XA-type structure, and the magnetic state is ferrimagnetic (FIM) at each equilibrium lattice constant. The total magnetic moments are mainly contributed by Mn atoms due to its strong exchange splitting. For Ga2MnY and Ga2MnLu, the magnetic states between ferromagnetic (FM) state and FIM state alternately appear with increasing crystal constant. Potential martensitic transformation can be gained due to the proper thermodynamic driving force (negative values of ΔE) and c/a, together with the analysis of phonon spectra, by considering the tetragonal distortions of cubic Ga2MnTM (TM = Sc, Y, Lu). The energy minima locate at c/a = 1.29, 1.21, 1.27, respectively. The three alloys in martensitic state show different variations of total magnetic moments and still maintain FIM state with changing c/a. The martensitic transformation and abundant changes in magnetic states motivate researchers to further explore new Z2-based Heusler alloys.

Tuning the magnetic properties of Fe3GeTe2 by doping with 3d transition-metals

Doping with alien transition-metal atoms is an effective method to tune the magnetic properties of two-dimensional magnetic material Fe3GeTe2. Using first principles calculation, we investigated the magnetic properties of Fe3GeTe2 doped with 3d atoms such as V, Cr, Mn, etc. Calculation results indicate that site I is more energetically favorable than site II for all 3d atoms, except for Co-doped Fe3GeTe2. Doping of these 3d atoms leads to significant variations of the average magnetic moment of FeI and FeII atoms. The magnetic moment of FeI decreased substantially for all 3d atom-doped-Fe3GeTe2 systems, except for the Co-doped system. Compared to FeI, the magnetic moment of FeII is more sensitive to doping with 3d-atoms. The observed variations of the magnetic moment can be explained by the electron-transfer of the doped atoms. These results can aid future experimental studies and provide valuable information for the development of Fe3GeTe2-based spin electronic devices.

Impact of Sn4+ substitution in Mg–Zn ferrites: Deciphering the structural, morphological, dielectric, electrical and magnetic properties

From the viewpoint of enormous applications and research, ferrite materials have already been achieved the status of one of the important branches of materials science. In this report, we have tuned the physical properties of Mg–Zn ferrites by Sn substitution investigated using X-ray diffraction, field emission scanning electron microscopy (FESEM), Fourier Transform Infrared (FTIR) spectroscopy, electrical and dielectric properties and quantum design physical properties measurement system. The Mg0·5Zn0.5SnxFe2-xO4 (0 ≤ x ≤ 0.10) samples have been synthesized by the conventional ceramic technique. The studied ferrites exhibits the single-phase up to x = 0.08 where an increase in lattice constant was observed. The FESEM images revealed the microstructure and the energy dispersive spectroscopy (EDS) confirms the absence of any unwanted elements. The increase (decrease) in bulk density (porosity) was associated with the variation of average grain size. FTIR spectra confirmed the formation of spinel structure. The dielectric polarization or conduction mechanism in these materials is due to the hopping of charge carriers at the octahedral sites. The common dielectric behavior of studied compositions is also observed. The substitution of Sn ions leads to enhanced dielectric constant and ac conductivity due to increased hopping of charge carriers. Complex impedance spectroscopy study revealed the non-Debye type of relaxation process within the studied compositions with a dominant contribution from grain boundary resistance. The dynamic magnetic hysteresis loops are measured to obtain the magnetic parameters. The low values of coercivity revealed the soft magnetic nature of the studied compositions. The obtained saturation magnetization (Ms) for Mg–Zn ferrite (x = 0.00) is comparable with the prior result. Non-linear decrease of Ms (62-44 emu/g) due to Sn substitution is explained based on the variation of magnetic moments over A- and B-sites. The squareness ratio (Mr/Ms) revealed that the magneto-statical interaction is present within the synthesized samples. The constant value of initial permeability (μʹ) over a wide range of frequencies revealed the compositional stability and quality of the prepared ferrite. The variation of μʹ with Sn content is similar to that of Msvs Sn contents. Moreover, theoretical cation distribution and the effect of Sn substitution on the related parameters have also been studied. The studied parameters are compared with the reported results, where available.

Study of magnetic and dielectric properties of ZnFe2O4/CoCr2O4 nanocomposites produced using sol-gel and hydrothermal processes

In this work, zinc ferrite (ZnFe2O4) and cobalt chromite (CoCr2O4) nanoparticles were synthesized using sol-gel process and hydrothermal method, respectively. The two different materials were mixed by physical means such that the final ratio (by weight) of the resulting nanocomposites (ZnFe2O4:CoCr2O4, abbreviated as ZF:CC) were 3ZF-CC, ZF-CC and ZF-3CC. The x-ray diffraction patterns of the ZnFe2O4 and CoCr2O4 nanoparticles confirmed the formation of the spinel structure, whereas the average crystallite size values computed using the Scherrer equation were found to be 43 and 57 nm, respectively. Scanning electron microscope (SEM) examination of the nanocomposites confirmed the nonspherical shape of the nanoparticles, homogenous dispersion, and larger grain size. The phase pure spinel structures of ZnFe2O4 and CoCr2O4 was confirmed from the fourier transform infrared spectroscopy (FTIR) analysis. Also, the composites formation did not influence any change in the functional groups. The dielectric properties, determined using LCR meter, exhibited non-repetitive behavior for the ZF-CC composite. The significant increase in the dielectric constant value was observed as the Fe2+↔Fe3+ and Cr2+↔Cr3+ transition due to electron transfer plays vital role in low frequency region, Also, explained by Maxwell-Wagner model. Moreover, the variation in experimental magnetic moments of ZF, CC and their nanocomposites (ZF-3CC, ZF-CC,3ZF-CC) were studied. VSM results revealed the change in behavior of magnetic nature of materials appreciably from pristine as magnetization was increasing and coercivity was decreasing with CC component and finally an optimized magnetic parameter values (Ms =51.20 emu/g and Hc =200 Oe) at ZF-CC were obtained.

Theoretical insights into magnetization in graphene containing single and interacting nanoporous defects

Defect-induced magnetism in two-dimensional materials continues to attract attention due to potential applications in spintronics. Using density-functional theory (DFT) approach, we report on the magnetization in graphene containing carbon vacancy defects, i.e., nanoporous graphene. We consider single nanopores consisting of up to ten vacancies and interacting nanopores consisting in vacancy pairs, divacancy pairs and vacancy-divacancy pairs, separated at varying distances. We found that the interactions between the nanopores weaken as their separation increases such that the formation energy tends to the value for the single nanopore while the magnetic moment tends to the sum of individual magnetic moments. Introducing additional nanopore to a pre-existing nanopore may enhance graphene's magnetic moment, however, the nanopores may also interact to induce zero magnetization. The enhancement, reduction or total annihilation of the magnetic moments may be adduced to interactions between the individual nanopores resulting in the saturation of the dangling bonds and/or the realignment of the electrons responsible for the magnetization. Also, our calculated values of induced magnetic moment of different single nanopores enable us to determine an empirical model for predicting the total magnetic moment as a function of nanopore size. The model is able to produce the magnetic moment of small and large nanopore sizes which are in excellent agreement with the DFT calculated values. Finally, we found our results to be consistent with recent experimental studies on magnetic response of graphene containing vacancies introduced via a synthesis process or ion irradiation, respectively. • An empirical model which captures the variation of magnetic moment with the number of vacancies in graphene is proposed. • Interactions between nanopores weaken as their separation increases. • Introducing additional nanopores to a pre-existing one in graphene may enhance, reduce or annihilate its magnetic moment. • Zero magnetization in porous graphene may be due to strong inter-pore interactions and the saturation of dangling bonds. • Our theoretical results support recent magnetic measurements in synthesized graphene containing vacancies.