Magnetoelectric Research Articles

Magnetoelectric effect of PZT/Ni50.5Mn27.9Ga21.6/PZT laminate composite: design and measurement

In this work we designed an experimental setup based on a double coil and an electromagnet to measure the magnetoelectric effect of a PZT/Ni50.5Mn27.9Ga21.6/PZT laminate composite, made of a bulk single crystal of Ni50.5Mn27.9Ga21.6 shape memory alloy. The shape memory alloy showed a martensitic transformation at 298 K, a Curie temperature at 368 K and room temperature magnetization of 2.87 uB/f.u. Strain response was found to be between 3% and 4% for magnetic fields greater than or equal to 4 kOe. As for the magnetoelectric effect, the induced voltages were moderate, increasing linearly with the frequency. There was a slight change in the magnetoelectric response with the DC applied magnetic field. For low frequencies, the magnetoelectric voltage was on the order of 10 mV and for higher frequencies about 50 mV. The best magnetoelectric coefficient (215 mV/cmOe) was obtained under an AC field of 1 Oe and a static magnetic field of 7 kOe.

Spontaneous Inversion Symmetry Breaking and Emergence of Berry Curvature and Orbital Magnetization in Topological ZrTe_{5} Films.

ZrTe_{5} has recently attracted much attention due to the observation of intriguing nonreciprocal transport responses which necessitate the lack of inversion symmetry (I). However, there has been debate on the exact I-asymmetric structure and the underlying I-breaking mechanism. Here, we report a spontaneous I breaking in ZrTe_{5} films, which initiates from interlayer sliding and is stabilized by subtle intralayer distortion. Moreover, we predict significant nonlinear anomalous Hall effect (NAHE) and kinetic magnetoelectric effect (KME), which are attributed to the emergence of Berry curvature and orbital magnetization in the absence of I symmetry. We also explicitly manifest the direct coupling between sliding ferroelectricity, NAHE, and KME based on a sliding-dependent k·p model. By studying the subsurface sliding in ZrTe_{5} multilayers, we speculate that surface nonlinear Hall current and magnetization would emerge on the natural cleavage surface. Our findings elucidate the sliding-induced I-broken mechanism in ZrTe_{5} films and open new avenues for tuning nonreciprocal transport properties in Van der Waals layered materials.

Core and surface structure and magnetic properties of mechano-synthesized LaFeO3 nanoparticles and their Eu3+-doped and Eu3+/Cr3+-co-doped variants

The core and surface structure and magnetic properties of mechano synthesized LaFeO3 nanoparticles (30–40 nm), their Eu3+-doped (La0.70Eu0.30FeO3), and Eu3+/Cr3+ co-doped (La0.70Eu0.30Fe0.95Cr0.05O3) variants are reported. Doping results in a transition from the O′-type to the O-type distorted structure. Traces of reactants, intermediate phases, and a small amount of Eu2+ ions were detected on the surfaces of the nanoparticles. The nanoparticles consist of antiferromagnetic cores flanked by ferromagnetic shells. The Eu3+ dopant ions enhance the magnetization values relative to those of the pristine nanoparticles and result in magnetic susceptibilities compatible with the presence of Eu3+ van Vleck paramagnetism of spin–orbit coupling constant (λ = 363 cm−1) and a low temperature Curie–Weiss like behavior associated with the minority Eu2+ ions. Anomalous temperature-dependent magnetic hardening due to competing magnetic anisotropy and magnetoelectric coupling effects together with a temperature-dependent dopant-sensitive exchange bias, caused by thermally activated spin reversals at the core of the nanoparticles, were observed.

The percolation inception of the CNT-polymer nanocomposites with the magneto-electric field effects on the CNT subbands

The percolation inception of CNT-polymer nanocomposites is studied considering the magneto-electric field effects on CNT subbands. The analytical model predicts the electrical conductivity where CNTs are modeled as slender rods with their geometric orientations as randomly distributed or aligned to transfer electrons at tunneling distance range. The tunneling effect takes into account the electron transmission between every linked pair of CNTs when evaluating electrical resistance. The subsequent CNT displacement computation and the resistance change comprise the other phase of the modeling approach. Piezoresistivity results of the analyses agree well with the experimental data when considering tunneling behavior in the percolation transition zone. The magnetic field enhances the field affected subbands and increases the electrical conductivity by enhancing the mobility of the charges. The results reveal that the efficiency of CNT network in transmitting charges is increased with higher aspect ratio CNTs that scaled the sensitivity to lower values.

Structural Optimization Design of Magnetoelectric Thin-Film Antenna for Bandwidth and Radiation Enhancement.

The acoustically actuated nanomechanical magnetoelectric (ME) antennas represent a promising new technology that can significantly reduce antenna size by 1-2 orders of magnitude compared to traditional antennas. However, current ME antennas face challenges such as low antenna gain and narrow operating bandwidth, limiting their engineering applications. In this paper, we enhance the bandwidth and radiation performance of ME antennas through structural optimization, leveraging theoretical analysis and numerical simulations. Our findings indicate that optimizing the inner diameter of the ring-shaped ME antenna can elevate the average stress of the magnetic layer, leading to improved radiation performance and bandwidth compared to circular ME antennas. We establish an optimization model for the radiation performance of the ME antenna and conduct shape optimization simulations using COMSOL Multiphysics. The results of the Multiphysics field optimization align with the stress concentration theory, demonstrating a strong correlation between the radiation performance and bandwidth of the ME antenna with the average stress of the magnetic film. The resonant frequency in the thickness vibration mode is determined to be 170 MHz. Furthermore, shape optimization can enhance the bandwidth by up to 104% compared to circular ME antenna structures of the same size.

Enhanced magnetic property and magnetodielectric coupling effect in multiferroic Gd2BaCuO5 via Zn2+ doping

The multiferroics with remarkable magnetoelectric (ME) coupling and technological application have drawn significant attention. Here, we report a chemical doping tunable effect on the magnetic, ferroelectric, and dielectric properties in type-II multiferroic Gd2BaCuO5. The magnetic measurement results show that a long-range antiferromagnetic ordering forms at the Néel temperature (TN1) of ∼12.1 K, and a second magnetization anomaly occurs at a lock-in transition temperature (TN2) of ∼6.4 K. Sharp peaks in the pyroelectric and dielectric curves are observed at the magnetic transition temperatures, indicating intrinsic coupling between magnetic and ferroelectric orderings. The doping of Zn2+ results in a gradual enhancement of magnetization due to the increase of uncompensated spins, and large magnetodielectric (MD) coupling parameter up to ∼7.65 % is obtained in Gd2BaCu0.7Zn0.3O5 because of strong spin-phonon coupling. The ferroelectric property is weakened in Zn2+ doped samples, suggesting the critical role of the 4f-3d magnetic interactions in determining the ME coupling effect. Moreover, an effective manipulation of electric field on magnetization is observed in Gd2BaCuO5. This work helps understand the importance of 4f-3d magnetic interactions in inducing ferroelectricity and explore the ME and MD coupling effects with multiple magnetic orderings.

Observation of Magnetic Field‐Induced and Partially Switchable Electric Polarization in Spin‐Chain FePbBiO4

AbstractThe linear magnetoelectric (ME) characteristics of a quasi‐1D spin‐chain compound, FePbBiO4, are reported. Two distinct antiferromagnetic (AFM) orders occurring at ≈23 K (TN1) and 12 K (TN2) are verified using magnetization, specific heat, and conspicuous dielectric (ε′) anomalies. A striking observation is that no pyrocurrent (Ipy) is detected in the absence of magnetic field (H); however, H‐induced ferroelectric polarization (P) at TN1 and P unexpectedly partially switches or reverses below TN2 as reproduced by applying positive and negative electric fields (E). The resulting magnetic field and temperature (H‐T) phase diagram illustrates T‐dependent H‐induced spin reorientation and electric P. The interaction between T, H, spin dynamics, and lattice structures is pivotal and is qualitatively discussed and proposed as an explanation for the observed ME nature.

Symmetry, topology, and geometry: The many faces of the topological magnetoelectric effect

A delicate tension complicates the relationship between the topological magnetoelectric effect (TME) in three-dimensional (3D) Z2 topological insulators (TIs) and time-reversal symmetry (TRS). TRS underlies a particular Z2 topological classification of the electronic ground state of crystalline band insulators and the associated quantization of the magnetoelectric response coefficient calculated using bulk linear-response theory but, according to standard symmetry arguments, simultaneously forbids a nonzero magnetoelectric coefficient in any physical finite-size system. This contrast between theories of magnetoelectric response in formal bulk models and in real finite-sized materials originates from the distinct approaches required to introduce notions of (electronic) polarization and orbital magnetization in these fundamentally different environments. In this work we argue for a modified interpretation of the bulk linear-response calculations in nonmagnetic Z2 TIs that is more plainly consistent with TRS and use this interpretation to discuss the effect's observation—still absent over a decade after its prediction. Our analysis is reinforced by microscopic bulk and thin-film calculations carried out using a simplified but still realistic effective model for the well established V2VI3 [V=(Sb,Bi) and VI=(Se,Te)] family of nonmagnetic Z2 TIs. When a uniform dc magnetic field is included in this model, the anomalous n=0 Landau levels (LLs) play the central role, both in thin films and in bulk. In the former case, only the n=0 LL eigenfunctions can support a dipole moment, which vanishes if there are no magnetic surface dopants and is quantized in the thick-film limit if magnetic dopants at the top and bottom surfaces have opposite orientation. In the latter case, the Hamiltonian projected into the n=0 LL subspace is a one-dimensional Su-Schrieffer-Heeger model with ground-state polarization that is quantized in accordance with the bulk linear-response coefficient calculated for (a lattice regularization of) the starting 3D model. Motivated by analytical results, we conjecture a type of microscopic bulk-boundary correspondence: a bulk insulator with (generalized) TRS supports a magnetoelectric coefficient that is purely itinerant (which is generically related to the geometry of the ground state) if and only if magnetic surface dopants are required for the TME to manifest in finite samples thereof. We conclude that in nonmagnetic Z2 TIs the TME is activated by magnetic surface dopants, that the charge-density response to a uniform dc magnetic field is localized at the surface and specified by the configuration of those dopants, and that the TME is qualitatively less robust against disorder than the integer quantum Hall effect. Published by the American Physical Society 2024

Resonance behaviour of magnetoelectric (PSLZT multilayer - NZFO) layered composites: A comprehensive theory – Experimental perspective

In recent years, compact antenna and miniaturized power transfer devices are among the interesting applications of magnetoelectric (ME) composites in low frequency (LF) / very low frequency (VLF) range. Here we elucidate, in general, analytical calculations used to understand, the vibrational modes and resonance frequencies of the layered ME composite and; Finite Element Analyses (FEM) with isotropic and anisotropic properties to accurately predict the resonance frequencies pertaining to the axisymmetric and asymmetric mode of vibrations with respect to significant ME response. Further, ME coefficient of the composite with Longitudinal - Transverse (L-T) configuration based on the interface coupling model were utilized to completely study the ME composites. The configuration optimized through the design was in particular corroborated experimentally with a representative PSLZT multilayer on NZFO based ME layered composite system. The PSLZT multilayer on NZFO based ME composite was fabricated by tape casting the constituent thick films and co-sintering process which are further analysed for their ME responses at their resonance frequencies. ME voltage spectrum showed a maximum of 7.74 V/cm.Oe at its axisymmetric resonance mode at 30.6 kHz. Various peaks at different resonance frequencies with respect to axisymmetric and asymmetric modes of vibrations agree well and validates the above modeling studies. Overall, the complete study provides a systematic design guideline for optimizing the ME composite configuration suitable for specific application with required resonance frequency.

Remotely Controlled Surface Charge Modulation of Magnetoelectric Nanogenerators for Swift and Efficient Drug Delivery.

We have developed a highly efficient technique of magnetically controlled swift loading and release of doxorubicin (DOX) drug using a magnetoelectric nanogenerator (MENG). Core-shell nanostructured MENG with a magnetostrictive core and piezoelectric shell act as field-responsive nanocarriers and possess the capability of field-triggered drug release in a cancerous environment. MENGs generate a surface electric dipole when subjected to a magnetic field due to the strain-mediated magnetoelectric effect. The capability of directional magnetic field-assisted modulation of the surface electrical dipole of MENG provides a mechanism to create/break ionic bonds with DOX molecules, which facilitates efficient drug attachment and on-demand swift detachment of the drug at a targeted site. The magnetic field-assisted drug-loading mechanism was minutely analyzed using spectrophotometry and Raman spectroscopy. The detailed time-dependent analysis of controlled drug release by the MENG under unidirectional and rotating magnetic field excitation was conducted using field-emission scanning electron microscopy, energy-dispersive X-ray, and atomic force microscopic measurements. In vitro, experiments validate the cytocompatibility and magnetically assisted on-demand and swift DOX drug delivery by the MENG near MCF-7 breast cancer cells, which results in a significant enhancement of cancer cell killing efficiency. A state-of-the-art experiment was performed to visualize the nanoscale magnetoelectric effect of MENG using off-axis electron holography under Lorentz conditions.

Enhancement of the magnetoelectric effect in the Bi2Fe4O9/BiFeO3 composite as a result of dipole and migration polarization in mullite

Enhancement of the magnetoelectric effect in the Bi2Fe4O9/BiFeO3 composite as a result of dipole and migration polarization in mullite

Realization of 2D multiferroic with strong magnetoelectric coupling by intercalation: a first-principles high-throughput prediction

The discovery of novel two-dimensional (2D) multiferroic materials is attractive due to their potential for the realization of information storage and logic devices. Although many approaches have been explored to simultaneously introduce ferromagnetic (FM) and ferroelectric (FE) orders into a 2D material, the resulting systems are often plagued by weak magnetoelectric (ME) coupling or limited room-temperature stability. Here, we present a superlattice strategy to construct non-centrosymmetric AM2X4 multiferroic monolayers, i.e., intercalating transition metal ions (A) into the tetragonal-like vacancies of transition metal dichalcogenide bilayers (MX2). Starting from 960 intercalated AM2X4 compounds, our high-throughput calculations have identified 21 multiferroics with robust magnetic order, large FE polarization, low transition barrier, high FE/FM transition temperature, and strong ME coupling. According to the origin of magnetism, we have classified them into twelve type-a, seven type-b, and two type-c multiferroics, which exhibit different ME coupling behavior. During the switching of polarization, the reversal of skyrmions chirality, the transition of the magnetic ground state from FM to antiferromagnetic, and the changes in spin-polarized electron distribution were observed in type-a, type-b, and type-c 2D multiferroic materials, respectively. These results substantially expand the family of 2D ferroic materials and pave an avenue for designing and implementing nonvolatile logic and memory devices.

Piezoelectric MEMS resonator with magnetic tip mass for energy harvesting from ultra-low intensity magnetic fields

This article addresses the limitation in the implementation of the Internet of Things (IoT) due to its energy dependence on batteries. The central focus of this work is the development and characterization of a magnetoelectric (ME) energy generator for IoT, which combines a piezoelectric microelectromechanical system (MEMS) with a magnetic mass to interact with ambient magnetic fields (MFs). The device's efficiency is validated through finite element modeling (FEM) simulations and electrical characterization. Its applicability in environments with residual magnetic fields, such as near common household appliances, highlights its viability. Specific results, such as a maximum generated power of 0.55 µW, corresponding to a power density of 9.19 µW/cm³, for a magnetic field strength of 5 µT, emphasize its ability to address energy challenges and promote the sustainable autonomy of IoT.

Theoretical Study of the Multiferroic Properties of Ion-Doped CaBaCo4O7

Using a microscopic model and Green’s function theory, we investigated the magnetization, specific heat, and polarization properties of CaBaCo4O7 (CBCO), scrutinizing their variations with temperature, magnetic field strength, and doping effects. Our analysis revealed a conspicuous kink in the specific heat curve near the critical temperature (TC), indicative of a phase transition. Additionally, the observed increase in polarization, P with escalating magnetic field strength serves as compelling evidence for the multiferroic nature of CBCO. Substituting Co ions with Fe ions resulted in an augmentation of the CBCO magnetization, M, while doping with Zn, Mn, or Ni ions led to a decline. Similarly, doping CBCO with Y or Sr ions at the Ca site exhibited divergent effects on magnetization, M, with an increase in the former and a decrease in the latter case. This modulation of the magnetization, M, can be attributed to the varying strains induced by the doping ions, thereby altering the exchange interaction constants within the system. The polarization, P, increases by Ni, Mn, or Zn substitution on the kagome layer Co sites. It can be concluded that Ni, Mn, or Zn doping enhances the magnetoelectric effect of CBCO. Notably, our findings align qualitatively well with experimental observations, reinforcing the validity of our theoretical framework.

Crafting very low frequency magnetoelectric antenna via piezoelectric and electromechanical synergic optimization strategy

A boom in exploration for marine geology and ocean resources has resulted in a huge demand for radio navigation or special environment communications, in turn spurring the rapid development of portable underwater wireless communication technology. State of the art acoustic communication methods used today are plagued by substantial transmission delays, multipath effects, and doppler frequency shifts, among other challenges, thus impeding the advancement of underwater wireless communication technology. Low-frequency electromagnetic transmission has proven to be a prospective solution for underwater communication, but the conventional electrical antennas is too large for portable underwater wireless communication. Emergent magnetoelectric (ME) antennas driven by piezoelectric materials have become a promising solution for miniaturizing very low frequency (VLF) communication systems. Here, a theoretical model between the radiation performance and piezoelectric material properties of the ME antenna was conducted. Guide by the theory analysis, Pb(In1/2Nb1/2)O3-Pb(Mn1/3Sb2/3)O3-Pb(Zr0.49Ti0.51)O3 (PIN-PMS-PZT) piezoelectric ceramic simultaneous with high d33 and Qm (d33 ∼ 401, Qm ∼ 1510) has been designed to enhance the magnetoelectric radiation of the VLF ME antenna. The PIN-PMS-PZT based ME antenna achieves a large converse magnetoelectric response 1.78 Gs·cm/V in EMR, which is almost doubled to commercial PZT based ME antenna. More importantly, a VLF communication system was built based on the VLF antenna, which successfully transmitted digital signals using Amplitude-Shift-Keying (ASK) modulation. It is believed that the presented work could provide a theoretical basis and feasible technical path for the employment of ME antennas in the future.

Modeling and radiation performance analysis of acoustically actuated magnetoelectric antennas

Bulk acoustic wave-mediated magnetoelectric (ME) antenna is the most promising acoustically actuated ultra-compact antenna scheme at ultrahigh frequency (0.3–3 GHz). However, the relevant research is still exploratory, and the antenna’s multi-field coupling modeling and performance analysis are imperfect. This work presents a cellular model based on finite element simulation to analyze the radiation characteristics of the ME antenna integrated on a thin-film bulk wave resonator (FBAR). Compared with the finite difference time domain (FDTD) method, the cellular model has the advantages of simplicity and high universality. The effects of mechanical and dielectric losses of piezoelectric (PE) material and mechanical and eddy current losses of magnetostrictive (MS) material on radiation efficiency are analyzed through the intensive research of unit cells of four different material combinations. Results show that the mechanical quality factors and piezomagnetic stress constant are the key parameters to determine the radiation efficiency. Besides conductivity and permeability, eddy current loss is also closely related to the thickness of the MS layer. This study provides a theoretical foundation for enhancing the radiation performance of ME FBAR antennas and identifying areas for further development.

Competition between external and internal electric fields induced multiple transitions of pole and pyroelectric currents in tetracobalt diniobate

Thermally stimulated depolarization current (TSDC) related internal electric field (Eint) is found to influence the pyrocurrent of multiferroics greatly, but its effect on the pole current of magnetoelectric (ME) materials has never been studied. In this article, ME antiferromagnet tetracobalt diniobate is cooled under an external electric field (Eext) from 125 K to generate the TSDC related Eint. Under a magnetic field (H), the pole current while cooling in the presence of Eint and Eext, and the subsequent pyrocurrent while heating without applying Eext is studied. Competition between Eext and Eint induces multiple transitions of pole current, and some transitions gradually disappear with increasing H. The pyrocurrent shows three transitions that are ascribed to the domain switching by Eint, depolarization of negative and positive domains, respectively. With increasing H, the transition at the highest temperature gradually disappears, indicating that the polarization is easier to be switched under a stronger H, which is explained both from the aspects of electrostatic potential energy and the special magnetic structure responsible for magnetoelectricity.

A novel MRI-based tumor-targeting theragnostic agent: Magnetoelectric nanoparticles in an in vivo murine KRAS/P53 pancreatic flank tumor model.

3075 Background: Magnetoelectric nanoparticles (MENPs) are a novel material with a magnetoelectric (ME) property that allows for conversion of an external magnetic field to a local electric field (EF) that can be exploited to generate a Coulomb force to target and electroporate the relatively non-polarized tumor cell walls. We hypothesized that their local EF and superparamagnetic cores can be exploited as an MRI-based anti-cancer theragnostic agent for solid tumors. Methods: 35 immunocompetent C57BL/6 mice were inoculated with KPC961 pancreatic adenocarcinoma cells in their flank. The 27 mice with the largest tumors at 4 weeks were randomized into 5 cohorts based on treatment: 300 µg of MENP (300; n=6), 600 µg of MENP (600; n=6), 300 µg of low-ME coefficient MENP (LM; n=5), 300 µg of MENP without M1 MRI (NM; MRI field control, n=5), and normal saline (NS; MENP causal effect control; n=5). The 300, 600, LM, and NS cohorts had T2 MRI maps (M0) on a 7T MRI. NM had T2 weighted MRIs at M0. All mice had a neodymium magnet placed over their tumors for 12 hours after tail vein injections (300 µl for all mice) for targeting. The 300, 600, LM, and NS cohorts then underwent MRI mapping (M1) after magnet removal (No M1 MRI for NM). MRI mapping was repeated 5 days after (M2). NM had a T2 weighted MRIs at M2. M1 and M2 data were used to assess relaxation time (contrast effect) and tumor volume from M0, respectively. Student t and ANOVA tests were used to compare differences for tumor volume and relaxation time data and one-sided Fisher’s exact test was used for complete response (CR) data. Results: The median M0 tumor volume was 109.6 mm3 for all mice, and there were no differences between any cohort ( p = 0.978; Table). The 300 and 600 MENP cohorts demonstrated a 102.7% reduction in volume (M2/M0; 56.7% vs. 159.4% for NS and NM controls, p = <0.001) and a 7.2% T2 negative contrast effect (M1/M0; 94.2% vs. 101.3% for NS, p = 0.046) compared to controls. Six mice in 300, 600, and LM (2 each) achieved a clinical CR (between 1 to 2 weeks after M1) vs. none in the NS and NM control cohorts ( p = 0.0418), without any recurrences until end of study (6 weeks after M2). Conclusions: This is the first report demonstrating the theragnostic effects of MENPs having both T2 contrast and locally ablative therapy properties as an in vivo tumor targeting agent. These results confirm prior pilot study and point towards irreversible electroporation as the likely mechanism of action (MOA) since the antitumor effect is not seen within the NM cohort. Additional studies characterizing the MOA, dose-response relationships, and immunomodulatory effects are needed to better understand their full clinical potential.[Table: see text]

Ultrafast light-induced magnetization in non-magnetic films: from orbital and spin Hall phenomena to the inverse Faraday effect

The field of orbitronics has emerged with great potential to impact information technology by enabling environmentally friendly electronic devices. The main electronic degree of freedom at play is the orbital angular momentum, which can give rise to a myriad of phenomena such as the orbital Hall effect (OHE), torques and orbital magnetoelectric effects. Here, we explore via realistic time-dependent electronic structure simulations the magnetic response of a non-magnetic material, an ultrathin Pt film, to ultrafast laser pulses of different polarizatons and helicities. We demonstrate the generation of significant orbital and spin magnetizations and identify the underlying mechanisms consisting of the interplay of the OHE, inverse Faraday effect and spin-orbit interaction. Our discoveries advocate for the prospect of encoding magnetic information using light in materials that are not inherently magnetic.

Surface Magnetization in Antiferromagnets: Classification, Example Materials, and Relation to Magnetoelectric Responses

We use symmetry analysis and density-functional theory to determine and characterize surface terminations that have a finite equilibrium magnetization density in antiferromagnetic materials. A nonzero magnetic dipole moment per unit area or “surface magnetization” can arise on particular surfaces of many antiferromagnets due to the bulk magnetic symmetries. Such surface magnetization underlies intriguing physical phenomena like interfacial magnetic coupling and can be used as a readout method of antiferromagnetic domains. However, a universal description of antiferromagnetic surface magnetization is lacking. We first introduce a classification system based on whether the surface magnetization is either sensitive or robust to roughness and on whether the magnetic dipoles at surface of interest are compensated or uncompensated when the bulk magnetic order is retained at the surface. We show that roughness-sensitive categories can be identified by a simple extension of a previously established group-theory formalism for identifying roughness-robust surface magnetization. We then map the group-theory method of identifying surface magnetization to a novel description in terms of bulk magnetic multipoles, which are already established as symmetry indicators for bulk magnetoelectric responses at both linear and higher orders. We use density-functional calculations to illustrate that nominally compensated surfaces in magnetoelectric Cr2O3 and centrosymmetric altermagnetic FeF2 develop a finite magnetization density at the surface, in agreement with our predictions based on both group theory and the ordering of the bulk multipoles. Our analysis provides a comprehensive basis for understanding the surface magnetic properties and their intimate correspondence to bulk magnetoelectric effects in antiferromagnets and has important implications for technologically relevant phenomena such as exchange-bias coupling. Published by the American Physical Society 2024