Spin Polarization Research Articles

Observation of field-free spin–orbit torque switching in a single crystalline (Ga,Mn)(As,P) ferromagnetic film with perpendicular anisotropy

We report the observation of field-free spin–orbit torque (SOT) magnetization switching in a single layer of (Ga,Mn)(As,P) ferromagnetic film exhibiting perpendicular magnetic anisotropy. The SOT switching phenomenon is characterized by distinct transitions between two Hall resistance (HR) states during current scans. When subjected to an in-plane bias field, the observed switching chirality in the HR hysteresis loop consistently aligns with SOT induced by spin polarization arising from Rashba- and Dresselhaus-type spin–orbit fields within the tensile-strained crystalline structure of the (Ga,Mn)(As,P) film. Remarkably, in the present experiments, we observe SOT switching even in the absence of an external bias field, and with its chirality depending on the direction of initial magnetization. We attribute this field-free switching to symmetry breaking facilitated by an internal coupling field, the orientation of which is determined by the external field experienced as the magnetization is initialized. Further evidence supporting the presence of such a coupling field includes a shift in the field-scan HR hysteresis depending on the direction of initialized magnetization. Structural analysis reveals a surface layer enriched in Mn and O, indicating the presence of oxide-based magnetic structures that are magnetically coupled to the (Ga,Mn)(As,P) film. The temperature dependence of field-free SOT switching corroborates this explanation, as the internal coupling field disappears above 40 K, consistent with the expected magnetic transition of the Mn3O4 structure. Our discovery of field-free SOT magnetization switching in a single-layer film represents a significant advancement, offering a novel pathway for the development of simpler and more energy-efficient spintronic devices.

Theoretical studies on the scattering of e± off the C2H2 molecule

Abstract By employing previous models [15,18], we report the differential, integrated elastic, inelastic, total (elastic+inelastic), viscosity and momentum transfer cross sections of e±- C2H2 collision dynamics, for the energy range of 1 eV-1 MeV. This report also incorporates Sherman spin polarization function and total ionization cross section. This work provides the first comprehensive study of electron/positron scattering from C2H2 over such a wide energy range. A complex optical model potential (OMP) has been used to represent the projectile-atom interaction. Relativistic Dirac equation has been solved, to get phase-shifts, needed for the calculations of scattering observables, using OMP. Our results are compared with the existing experimental data and theoretical calculations.

Magnonic superconductivity.

We uncover a superconducting state with partial spin polarization induced by a magnetic field. This state, which we call "magnonic superconductor," lacks a conventional pairing order parameter but is characterized instead by a composite order parameter that represents the binding of electron pairs and magnons. We rigorously demonstrate the existence of magnonic superconductivity with high transition temperature in one-dimensional and two-dimensional Hubbard models with repulsive interaction. We further show that magnonic Cooper pairs can attract to form higher-charge bound states, which can give rise to charge-6e superconductivity.

Spin injection from a magnetically near-compensated state in GdFeCo and inverse spin Hall effect in electron–hole compensated metal YH2

Rare-earth-transition-metal (RE-TM) ferrimagnets are excellent materials for spin encode/decode operations via spin transport in nonmagnetic regions. This superior performance stems from two key factors. First, the antiferromagnetic coupling between RE4f and TM3d sublattices reduces both the spin-transfer-torque switching time and inter-device magnetic-coupling. Second, the RE-TM ferrimagnets function as spin injectors/ejectors, with the TM3d sublattice solely responsible for carrier spin polarization (p), similar to conventional ferromagnetic metals. We performed spin transport experiments using the sign change ofpin RE-TM, which exhibits a positive value above the magnetization compensation temperature and a negative value below it. We measured temperature dependencies of the transverse resistances (RT) of electron-hole compensated metal YH2under out-of-plane spin-polarized current injection/ejection from GdFeCo (Gd:Fe:Co = 25:66:9). The abrupt change in loop polarity of the out-of-plane field dependence ofRTin YH2between 290 and 300 K, which aligns with the out-of-field curve of the polar Kerr rotation in GdFeCo electrodes, strongly suggests that the observedRTresults from the inverse spin Hall effect (ISHE) in YH2. We analytically formulated ISHE in terms of the electron and hole spin currents injected from the spin sources, enabling regression analysis to assess the spin transport characteristics of a GdFeCo/YH2/GdFeCo magnetic double heterostructure. To explain the observed Hall voltages, enhancements in both the spin diffusion length of YH2and the spin injection efficiency are necessary.

Spin-Selective Charge Transfer-SERS Driven Label-Free Enantioselective Discrimination of Chiral Molecules on Ag Nanoparticle-Decorated Ni Nanorod Arrays.

Enantioselective discrimination is critical in several fields, particularly in pharmaceutics and clinical drug research. Chiral molecules possess unique charge transfer properties, showing an enantioselective preference for electron spin orientation when interacting with the magnetic surface. Here, we developed spin-selective charge transfer (SSCT)-based label-free surface-enhanced Raman scattering (SERS) achiral magnetic substrates for the enantioselective discrimination of chiral molecules without creating asymmetric chiral adsorption sites. The e-beam-based glancing angle deposition (GLAD) technique was utilized to construct achiral magnetic surface-enhanced Raman scattering (SERS) substrates by decorating Ag nanoparticles over Ni nanorods. SERS spectroscopy was carried out on significant enantiomers, including cystine, alanine, and DOPA (l-3-(3,4-dihydroxyphenyl) alanine). An external electromagnet was used to manipulate the magnetic substrate's spin polarization by altering the magnetic field's direction. Subsequently, SERS spectra were acquired. Based on the magnetic field's direction, there is a complementary variation in the intensities of SERS spectra of the enantiomers. The SSCT process between molecule-metal complexes synergized with the magnetic field direction to control the electron spin, leading to SERS-based enantioselective discrimination. This label-free, easy, yet practical approach offers a characteristic paradigm shift from the recent complex approaches for chiral detection and separation.

Study on the photoelectric and electromagnetic properties of nonmetal elements X(X=B, C, N) doping bilayer CdS

In this paper, the electronic, magnetic and optical properties of nonmetal elements doping BL-CdS systems are calculated by DFT + U. The stable structures of nonmetal elements doping BL-CdS are obtained by calculating Ef. The analysis of electronic structures indicates that BL-CdS is semiconductor with direct band gap 2.56eV. The 2B@2S and 2C@2S systems exhibit semiconductor characteristics. B@S, C@S, N@S and 2N@2S systems present magnetic semiconductor properties and magnetism mainly comes from the spin polarization of impurity atoms. Cd atoms lose electrons, S and impurity atoms get electrons. With increase in the number of impurity atoms, number of electrons obtained is gradually increasing. The work function of BL-CdS is 6.26eV. B@S and 2C@2S have the smaller work function, indicating that two systems have higher electron mobility. The calculation of optical properties shows that BL-CdS has good photoelectric properties in visible light and the doping systems have better photoelectric properties in ultraviolet region or infrared region. ML-CdS, BL-CdS, 2B@2S systems show high performance of photocatalytic water splitting. The research results provide ideas for nano-spintronic devices and photodetectors.

Dynamical induced quark spin polarization by magnetic field at the early stage of heavy-ion collisions

Dynamical induced quark spin polarization by magnetic field at the early stage of heavy-ion collisions

Nearly perfect spin polarization of noncollinear antiferromagnets

Ferromagnets with high spin polarization are known to be valuable for spintronics—a research field that exploits the spin degree of freedom in information technologies. Recently, antiferromagnets have emerged as promising alternative materials for spintronics due to their stability against magnetic perturbations, absence of stray fields, and ultrafast dynamics. For antiferromagnets, however, the concept of spin polarization and its relevance to the measured electrical response are elusive due to nominally zero net magnetization. Here, we define an effective momentum-dependent spin polarization and reveal an unexpected property of many noncollinear antiferromagnets to exhibit nearly 100% spin polarization in a broad area of the Fermi surface. This property leads to the emergence of an extraordinary tunneling magnetoresistance (ETMR) effect in antiferromagnetic tunnel junctions (AFMTJs). As a representative example, we predict that a noncollinear antiferromagnet Mn3GaN exhibits nearly 100% spin-polarized states that can efficiently tunnel through low-decay-rate evanescent states of perovskite oxide SrTiO3 resulting in ETMR as large as 104%. Our results uncover hidden functionality of material systems with noncollinear spin textures and open new perspectives for spintronics.

Gate-tunable high tunneling magnetoresistance induced by hybrid interface states in Ni-electrode single-molecule junctions

Based on the density functional theory and non-equilibrium Green's function method, the modulation effects of gate voltage on the spin transport properties of Ni/triphenylene/Ni single-molecule junctions are investigated. The plane-, platform-, and tip-shaped electrode configurations are considered in the calculations. The numerical results show that the electrode configuration and gate voltage significantly influence the hybrid interface states (HIS) and further the spin transport properties of the molecular junctions. The molecular junctions with plane- and platform-shaped electrode configurations show weak spin polarization (SP) and tunneling magnetoresistance (TMR). Still, they exhibit excellent field effect transistor behaviors with the modulation of the gate voltage. Due to the delocalized spin-down HIS located at the Fermi level, the molecular junction with tip-shaped electrode configuration presents high and controllable SP and TMR behaviors through the gate voltage modulation. The calculations demonstrate that high spin-polarized HIS located at the Fermi level are extremely significant for the generation of excellent spin transport properties in molecular junctions composed of non-magnetic molecule and magnetic electrodes.

Dynamic nuclear polarization mechanism in isolated NV-centers at high magnetic fields

Nitrogen vacancy centers in diamonds are promising spin-based quantum sensors and qubits. These optically addressable paramagnetic point defects have the potential to allow efficient dynamic nuclear polarization (DNP) under ambient conditions due to their large electron spin polarization and long spin coherence time. NV-based DNP studies have shown significant sensitivity enhancement of 13C nuclear magnetic resonance (NMR). In this work, we present an analytical theory using a density matrix and average Hamiltonian theory for NV-13C spin system under varying magnetic fields, internal interaction strengths, and microwave irradiation parameters. We use a reduced basis approach under selective excitation of a single quantum transition in NV-center electron spin levels to derive the expressions for the matching conditions, effective Hamiltonian and polarization transfer frequency. Our results provide insight into the optimal experimental conditions for efficient DNP and the impact of the internal interactions on the DNP performance. The theoretical predictions are verified using numerical simulations.

Enhancing Electrocatalytic Activity through Tailored Charge and Spin Polarization in Molecules and Frameworks

Single-molecule and framework-based electrocatalysts are increasingly attractive in the field of electrocatalysis due to their precise atomic-level control and highly tunable properties, enabling the development of highly efficient and selective energy conversion processes. Tailoring charge and spin polarization within these structures presents a unique opportunity to significantly enhance catalytic activity, opening new avenues in developing efficient electrocatalytic systems. This presentation will outline methods our group has developed to synthesize and adjust charge and spin configurations in molecular and framework catalysts. We will explore a variety of pathways, including the design of single molecular catalysts with optimized spin states, the application of mesomeric and inductive effects for charge regulation, and the use of external magnetic fields and chirality to modulate spin polarization at the molecular level. Our findings indicate that such customization can accelerate the kinetics of spin-sensitive electrochemical reactions like oxygen electrocatalytic reactions. Furthermore, we will discuss how the inherent properties of the catalysts, particularly magnetic moments and spin-orbit interactions, play a crucial role in influencing catalytic performance in the presence of spin potentials. Hence, this presentation aims to provide an overview of our advanced strategies to reconfigure charge and spin states in framework and molecular catalysts, underscoring their potential to revolutionize electrochemical energy conversion technologies.

Promoting the Radical-Mediated Pathway and Li₂S Conversion By N-Doped Carbon-Embedded Cobalt-Doped Titanium Nitride Electrocatalyst with High Donor-Number Solvent for Lean Electrolyte Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are recognized as some of the most promising candidates for next-generation batteries, owing to their high specific capacity, cost-effectiveness, and lightweight properties. Despite these advantages, the dissolution of the sulfur leads to the shuttling effect of long-chain lithium polysulfides (Li2Sx, 4≤x≤8). Moreover, the lean electrolyte system experiences a reduction in ionic transport due to the formation of ion-pairing and clusters of polysulfides. Therefore, the development of electrolytes that can stabilize the solvation structure of lithium-polysulfide and the introduction of electrocatalysts to suppress the shuttling effect are required for lean electrolyte lithium-sulfur batteries.High donor-number solvents can stabilize the Li+-solvated structure by effectively shielding the Li+ ion’s effective nuclear charge. This Li+-solvated structure, in coordination with high donor-number solvents, can effectively interact with tri-sulfur radicals and long-chain polysulfides, which possess relatively delocalized negative charges. As a result, a high donicity electrolyte can enhance sulfur utilization by increasing the solubility of polysulfides. However, the poor compatibility of high donor-number solvents with Li metal presents a challenge, making their excessive use impractical. Therefore, optimizing the amount of high donor-number solvent is essential. Through careful optimization, it is possible to achieve high donicity electrolyte conditions that are compatible with Li metal. The 1 vol% N,N-Dimethylacetamide (DMA) in 1,2-dimethoxyethane (DME)/1,3-dioxolane (DOL) co-solvent (DMA:DME:DOL=1:49.5:49.5 vol%) electrolyte achieved a higher discharge capacity after 20 cycles compared to both a low donicity (DME/DOL, 1:1 vol%) and a high donicity (DMA/DOL, 1:1 vol%) electrolyte. Electrolyte modification alone cannot completely suppress the shuttling effect, as the radical-mediated pathway activated by high donor-number solvent leads to the presence of tri-sulfur radicals. Recent research has investigated the ferromagnetic catalysts to enhance the adsorption of polysulfides through the Lorentz force and facilitate the conversion of Li2S with spin polarization in lithium-sulfur batteries. Introducing ferromagnetism through cobalt-doping into N-doped carbon embedded titanium nitride nanowires electrocatalysts could improve the adsorption of polysulfides and tri-sulfur radicals, as well as their conversion to Li2S and promote radical-mediated pathways with high donor-number solvents in lean electrolyte lithium-sulfur batteries. Consequently, N-doped carbon-embedded cobalt-doped titanium nitride nanowires on separator within the 1 vol% DMA electrolyte achieves a high discharge capacity of 454.8 mA h g−1 after 120 cycles with sulfur loading of 3.6 mg cm−2 and E/S ratio of 10 μL mg−1.

Theory of circular dichroism in angle- and spin-resolved photoemission from the surface state on Bi(111)

Circular dichroism (CD) of photoemission from a surface state on Bi(111) is considered within an ab initio one-step theory of photoemission. The symmetry of the azimuthal distribution of CD for different spin directions is discussed in terms of the spin structure of the initial states. Both normal and off-normal light incidence are considered. Strong photon energy dependence of photoemission in the ultraviolet range is observed. The principal difference between the initial state spin polarization and the spin photocurrent is emphasized and problems with revealing the orbital angular moment with photoemission are pointed to.

Nuclear Magnetic Resonance with a Levitating Microparticle.

Nuclear magnetic resonance (NMR) spans diverse fields from biology to quantum science. Employing NMR on a floating object could unveil novel possibilities beyond conventional operational paradigms. Here, we observe NMR within a levitating microdiamond using the nuclear spins of nitrogen-14 atoms. By tightly confining the angular degrees of freedom of the diamond in a Paul trap, we achieve efficient hyperfine interaction between optically polarized electronic spins of nitrogen-vacancy centers and the ^{14}N nuclear spin, enabling nuclear spin polarization and quantum state readout revealing coherence times up to hundreds of microseconds. This represents the longest recorded spin coherence time in a levitated system, surpassing previous records by 3 orders of magnitude. Our results offer promise for various applications, including cooling macroscopic particles to their motional ground state and exploring geometric phases for gyroscopy.

A Machine Learning Approach for Understanding the Oxygen Vacancy Formation Energies within DRX Cathode Structures

Disordered Rock-Salt (DRX) cathode structures are materials where lithium and transition metal atoms are arranged in a disordered solid solution. These structures are currently under intensive study [1] due to their potential higher energy density, bigger capacity than the typical layered cathode structure, and improved flexibility in the selection of raw materials. Driven by this, we have recently compiled a DFT-based database of DRX structures with over 6,000 different metal oxide compositions. Moreover, since oxygen loss is linked to voltage degradation, intergranular cracks, and irreversible phase transformation, developing a descriptor that allows us to understand and reflect the stability of oxygen within the DRX anion lattice is crucial. It represents a significant research challenge that our study aims to address.In this work, we study two things: First, since the generation of oxygen vacancies holds a critical value in elucidating the stability of cathode material oxides[2], our methodology focuses on generating an extensive DFT database of over 1,400 oxygen vacancy formation energies (Evf(O)) from selected DRX structures. We then employ a machine learning (ML) model to predict the Evf(O) and their distribution for a variety of different compositions. The ML model incorporates site-specific features, such as the maximum reduction potential of the cations neighboring the O vacancy, the O p-band center of mass, and information from atomic population analysis (such as the bond order and the bond spin polarization between each O and its nearest neighbors). This approach is necessary because the DRX structure contains different local environments where O vacancies could be created, and recent work from Baldassarri et al. has highlighted the limitations of ML models that only include global features and lack their ability to differentiate the behavior of compounds containing the same elements but in different oxidation states [3]. This allows us to predict the O vacancies energetics with an accuracy comparable to DFT and to develop a descriptor to classify different compositions of DRX structures.Second, given that oxygen destabilizes during delithiation, we analyze the impact and relationship of the Li vacancy formation energies (Evf(Li)) and Evf(O) of each O able to create a vacancy. The results show a strong interaction between these energetics, and in particular, an inverse correlation between Evf(O) of a specific O site and the Evf(Li) of the Li atoms that surround this O, which within these DRX prototypes the number of surrounding Li varies from 1 to 5. In line with what others proposed [4], there is a strong interaction between these two vacancy types. However, we expect that the generation of O vacancies is determined not only by their thermodynamic driving force but also by the displacement/migration of the nearest neighbor lithium (NN-Li) that surrounds each O.The methodology and fundamental understanding developed in this study about DRX O-vacancies and their relationship with NN-Li during delithiation could help investigate and describe compositionally similar transition metal oxide cathodes belonging to the same crystal structure family (layered, spinel-like, γ-LiFeO2). Hence, this research not only enhances our understanding of these materials but also paves the way for the design and development of more flexible and stable energy storage systems.[1] S. Anand, B. Ouyang, T. Chen, G. Ceder, Impact of the energy landscape on the ionic transport of disordered rocksalt cathodes, Physical Review Materials 7(9) (2023) 095801.[2] H. Zhang, B.M. May, F. Omenya, M.S. Whittingham, J. Cabana, G. Zhou, Layered Oxide Cathodes for Li-Ion Batteries: Oxygen Loss and Vacancy Evolution, Chemistry of Materials 31(18) (2019) 7790-7798.[3] B. Baldassarri, J. He, A. Gopakumar, S. Griesemer, A.J.A. Salgado-Casanova, T.-C. Liu, S.B. Torrisi, C. Wolverton, Oxygen Vacancy Formation Energy in Metal Oxides: High-Throughput Computational Studies and Machine-Learning Predictions, Chemistry of Materials 35(24) (2023) 10619-10634.[4] C. James, Y. Wu, B.W. Sheldon, Y. Qi, The impact of oxygen vacancies on lithium vacancy formation and diffusion in Li2-xMnO3-δ, Solid State Ionics 289 (2016) 87-94.

Two-Dimensional Rare-Earth-Based Half-Metals with Topological Bimerons.

Two-dimensional magnets with spontaneous topological spin textures have important application prospects in highly integrated spintronic devices. However, so far, the predicted two-dimensional magnets with topological spin textures are mainly based on transition metals, and most of them are semiconductors or metals. Here, based on first-principles calculations, we predict two-dimensional rare-earth-based half-metallic monolayer GdA2N4 (A = Ge, Sn), with 100% spin polarization. Spontaneous topological spin textures, i.e., bimeron clusters, are revealed in those monolayers due to the magnetic frustration and easy-plane magnetic anisotropy. The bimeron clusters can be efficiently tuned through biaxial strain and driven by in-plane spin-polarized current. These results underscore the promising potential of rare-earth-based two-dimensional half-metals for spintronic device applications.

First principle study of physical aspects and hydrogen storage capacity of magnesium-based double perovskite hydrides Mg2XH6 (X = Cr, Mn)

Hydrogen's potential as a clean energy source has propelled hydrogen storage into a pivotal realm of contemporary research. Cutting-edge double perovskite compounds have become a central focus for exploring hydrogen storage applications. The aim is to scrutinize their structural, mechanical, electronic, magnetic, thermoelectric, and hydrogen storage properties. The negative value of enthalpy of formation and approaching value of tolerance factor confirm the thermodynamic and structural stability of studied compositions, leading to the calculation of ground state lattice parameters. The high value of Curie temperature (310 K), particularly for Cr-based composition, exhibits the viable application of this composition at room temperature. Metallic behavior in the spin-up channel and semiconducting nature in the spin-down channel are witnessed in the band structure that ascertains the half-metallic behavior of both compositions, ensuring 100% spin polarization, an essential feature for spintronic devices. Furthermore, employing the BoltzTraP code to analyze thermoelectric characteristics with heightened Seebeck coefficients and reduced thermal conductivity reveals their suitability for thermoelectric devices. Moreover, investigation into the hydrogen storage characteristics of Mg2XH6 (X = Cr, Mn) exhibits notable hydrogen storage capacities of 5.60 wt% for Mg2CrH6 and 5.51 wt % for Mg2MnH6. This study marks the pioneering examination of Mg2XH6 (X = Cr, Mn) double perovskite-type hydrides, promising significant contributions to future research endeavours in hydrogen storage applications.

Handedness manipulation of propagating antiferromagnetic magnons

Antiferromagnetic magnons possess a distinctive feature absent in their ferromagnetic counterparts: the presence of two distinct handedness modes, the right-handed (RH) and left-handed (LH) precession modes. The magnon handedness determines the sign of spin polarization carried by the propagating magnon, which is indispensable for harnessing the diverse functionalities in magnonic devices, such as data encoding, magnon polarization-based logic systems, and quantum applications involving magnons. However, the control of coherently propagating magnon handedness in antiferromagnets has remained elusive. Here we demonstrate the manipulation and electrical readout of propagating magnon handedness in perpendicularly magnetized synthetic antiferromagnets (SAF). We find that the antiferromagnetic magnon handedness can be directly identified by measuring the inverse spin Hall effect (ISHE) voltage, which arises from the spin pumping effect caused by the propagating antiferromagnetic magnons in the SAF structure. The RH and LH modes of the magnon can be distinguishable when the SAF structure is sandwiched by heavy metals with the same sign of spin Hall angle. This work unveils promising avenues for harnessing the unique properties of antiferromagnetic magnons.

Efficient Transfer of Chirality in Complex Hybrid Materials and Impact on Chirality-induced Spin Selectivity.

Transfer of chirality, or transmission of asymmetric information from one system to another, plays an essential role in fundamental biological and chemical processes and, therefore, is essential for life. This phenomenon also holds immense potential in spintronics in the context of chirality-induced spin selectivity (CISS). In the CISS, the spatial arrangement of chiral molecules influences the spin state of electrons during the charge-transfer processes. Transfer of chirality from chiral molecules to an achiral material in a hybrid environment enables induction of spin polarization in the achiral material, thus vastly expanding the library of CISS-active electronic materials. Such "induced" CISS signals could have different responses compared to pure chiral molecules because the electronic properties of the achiral material come into play in the former case. In addition, multiple chiral sources can be used, which can have a nontrivial contribution to the induced CISS effect and can act either synergistically or antagonistically. This opens the way to achieving tunability of the CISS signals via chemical means. Earlier, such a chirality-transfer phenomenon and the resulting induced CISS effect were demonstrated in a hybrid system containing carbon nanotubes (CNTs) functionalized with a chiral agent (Fmoc-diphenylalanine l/d). In this context, we extend this result by investigating the role of an additional chiral moiety (l-lysozyme enzyme crystals) in this system. Here, the chiral crystal surrounds the chiral-functionalized CNTs, and we show that synergistic interactions result in more efficient chirality transfer, resulting in nontrivial changes in the CISS effect. This manifests in the form of (a) a stronger CISS signal compared to only one single chiral agent, (b) nonmonotonic temperature dependence and sign reversal of the CISS signal, and (c) persistence of the CISS signal at higher temperatures. Hybrid chiral materials with multiple chiral sources could, therefore, offer intricate control of the CISS signal via modification of its constituents, which is not possible in homogeneous chiral systems with single chiral sources.

Study of magnetic field error suppression methods based on atomic parameters of cell in atomic co-magnetometer rotation measurement

Abstract We propose a new model for magnetic field errors based on the rotation measurement of the K-Rb- 21 Ne co-magnetometer, considering the density ratio and spin collisions. The spin polarization characteristics of different alkali metal density ratios were analyzed by creating five cells with different density ratios, and the correctness of the magnetic field error model was verified experimentally. Moreover, the effects of five different alkali metal density ratios of cells on the sensitivity, long-term stability and magnetic field error suppression of the K-Rb- 21 Ne co-magnetometer were investigated experimentally. When the density ratio is 1:107, there can be the optimal magnetic field error suppression effect, sensitivity and long-term stability. According to the derived magnetic field error equation, the magnetic noise error of the K-Rb- 21 Ne co-magnetometer with an optimized density ratio is reduced by nearly 5 times from 260°/h/nT to 56.5°/h/nT, the sensitivity is improved from 2.9×10−5 °/s/Hz 1 / 2 to 7.0×10−6 °/s/Hz 1 / 2 at 1 Hz, and the long-term stability Allan variance over two hours is improved from 1.9×10−2 °/h to 8.9×10−3 °/h. This result provides a theoretical basis for designing the parameters of the K-Rb- 21 Ne co-magnetometer cell.