Magnetic Nanostructures Research Articles

Maneuvering the magnetic anisotropy in single-phase nanocrystalline α-FeCo via external static magnetic field assisted one dimensional growth

Magnetic anisotropy in magnetic nanostructures is highly desirable for the manufacturing of magnetic data storage devices. Therefore, in the present work, the effective magnetic anisotropy is investigated in α-FeCo nanoparticles (NPs) and nanowires (NWs) prepared using hydrazine reduction method. The growth of the NWs was manifested by applying external static magnetic field using bar magnets during synthesis which promoted the continuous growth up to 4 µm of average length and an average diameter of ~ 294 nm. The NP-formation as well as NW-growth adopted the phenomena of Ostwald ripening. The NWs demonstrated the enhanced saturation magnetization, enhanced effective magnetic anisotropy and reduced coercivity as compared to the corresponding NPs. The enhanced magnetic properties of the NWs have been associated with the magnetic force exerted by the external magnetic field during growth which aligned the crystallites along the direction of magnetic field together with the reorientation of the easy axis< 100 > of FeCo along the long axis of the wire. The assistance of the magnetic field during growth enhanced the ease of magnetization along the long axis of the wire. Additionally, the growth induced shape magnetic anisotropy via induced the dipolar interactions lead to the enhanced effective magnetic anisotropy. Thereby, it can be suggested that the external magnetic field applied during synthesis not only plays a primary role in the growth of NWs but also enhances the intrinsic magnetic properties of the material.

Enhancement of Exchange Bias and Perpendicular Magnetic Anisotropy in CoO/Co Multilayer Thin Films by Tuning the Alumina Template Nanohole Size.

The interest in magnetic nanostructures exhibiting perpendicular magnetic anisotropy and exchange bias (EB) effect has increased in recent years owing to their applications in a new generation of spintronic devices that combine several functionalities. We present a nanofabrication process used to induce a significant out-of-plane component of the magnetic easy axis and EB. In this study, 30 nm thick CoO/Co multilayers were deposited on nanostructured alumina templates with a broad range of pore diameters, 34 nm ≤ Dp ≤ 96 nm, maintaining the hexagonal lattice parameter at 107 nm. Increase of the exchange bias field (HEB) and the coercivity (HC) (12 times and 27 times, respectively) was observed in the nanostructured films compared to the non-patterned film. The marked dependence of HEB and HC with antidot hole diameters pinpoints an in-plane to out-of-plane changeover of the magnetic anisotropy at a nanohole diameter of ∼75 nm. Micromagnetic simulation shows the existence of antiferromagnetic layers that generate an exceptional magnetic configuration around the holes, named as antivortex-state. This configuration induces extra high-energy superdomain walls for edge-to-edge distance >27 nm and high-energy stripe magnetic domains below 27 nm, which could play an important role in the change of the magnetic easy axis towards the perpendicular direction.

Observation of Néel-type skyrmions in acentric self-intercalated Cr1+δTe2

Transition-metal dichalcogenides intercalated with 3d-transition metals within the van der Waals (vdW) gaps have been the focus of intense investigations owing to their fascinating structural and magnetic properties. At certain concentrations the intercalated atoms form ordered superstructures that exhibit ferromagnetic or anti-ferromagnetic ordering. Here we show that the self-intercalated compound Cr1+δTe2 with δ ≈ 0.3 exhibits a new, so far unseen, three-dimensionally ordered (2×2×2) superstructure. Furthermore, high resolution X-ray diffraction reveals that there is an asymmetric occupation of the two inequivalent vdW gaps in the unit cell. The structure thus lacks inversion symmetry, which, thereby, allows for chiral non-collinear magnetic nanostructures. Indeed, Néel-type skyrmions are directly observed using Lorentz transmission electron microscopy. The skyrmions are stable within the accessible temperature range (100–200 K) as well as in zero magnetic field. The diameter of the Néel skyrmions increases with lamella thickness and varies with applied magnetic field, indicating the role of long-range dipole fields. Our studies show that self-intercalation in vdW materials is a novel route to the formation of synthetic non-collinear spin textures.

(Invited) Magneto-Ionic Control of Heterostructures and Interfaces

Magneto-ionics has shown promise for energy-efficient nanoelectronics, where ionic migration can be used to achieve atomic scale control of interfaces in magnetic nanostructures, and in turn modulate a wide variety of functionalities. Recently, we have discovered that chemisorbed oxygen and hydrogen on the surface of ferromagnetic films can induce significant Dzyaloshinskii–Moriya interaction (DMI) [1], a handle to introduce topology into nanoscale magnets. This has enabled direct tailoring of skyrmions winding number as well as wall type at room temperature via oxygen chemisorption. We have also demonstrated a sensitive and reversible chirality switching of magnetic domain walls [2] and writing/deleting of skyrmions [3] via hydrogen chemisorption/desorption. These chemisorption induced magnetic effects on controlled ferromagnet surfaces offer an ideal platform to gain quantitative understanding of magneto-ionics at buried interfaces, where the ionic motion can be further controlled by an electric field [4]. These effects are relevant for 3-dimensional information storage as a potentially contactless way to address spin textures, such as in interconnected nanowire networks [5]. Interestingly, nanoporous metal foams made of random assemblies of nanowires have found applications in deep-submicron particulate filtration, relevant to combatting COVID-19 and air pollution. Such foams are efficient, breathable, light-weight, robust, and can be reused and recycled [6]. Our mask design based on such foams has been selected by BARDA-NIOSH as a Phase 1 Winner of the Mask Innovation Challenge [7].[1] Science Advances, 6, eaba4924 (2020).[2] Physical Review X, 11, 021015 (2021).[3] DOI: https://doi.org/10.21203/rs.3.rs-575830/v1[4] ACS Applied Materials and Interfaces, 13, 38916−38922 (2021).[5] Nano Letters, 21, 716-722 (2021).[6] Nano Letters, 21, 2968-2974 (2021).[7] https://drive.hhs.gov/mask_challenge.html.This work has been supported by the NSF (DMR-1905468, DMR-2005108, ECCS-1933527), the nCORE SMART center through SRC/NIST, the University of California and Georgetown University.

Unveiling the Complex Magnetization Reversal Process in 3D Nickel Nanowire Networks

AbstractUnderstanding the interactions among magnetic nanostructures is one of the key factors to predict and control the advanced functionalities of 3D integrated magnetic nanostructures. In this work, the focus is on different interconnected Ni nanowires forming an intricate, but controlled, and ordered magnetic system: Ni 3D Nanowire Networks (3DNNs). These self‐ordered systems present striking anisotropic magnetic responses, depending on the interconnections’ position between nanowires. To understand their collective magnetic behavior, the magnetization reversal processes are studied within different Ni 3D Nanowire Networks compared to the 1D nanowire 1DNW array counterparts. The systems are characterized at different angles using first magnetization curves, hysteresis loops, and First Order Reversal Curves techniques, which provided information about the key features that enable macroscopic tuning of the magnetic properties of the 3D nanostructures. In addition, micromagnetic simulations endorse the experiments, providing accurate modeling of their magnetic behavior. The results reveal a plethora of magnetic interactions, neither evident nor intuitive, which are the main role players controlling the collective response of the system. The results pave the way for the design and realization of 3D novel metamaterials and devices based on the nucleation and propagation of ferromagnetic domain walls both in 3D self‐ordered systems and future nano‐lithographed devices.

Bio-inspired computing with magnetic skyrmions using deep learning

Spintronic systems demonstrate significant value due to variety of features that can be used in bio-inspired computing applications. Skyrmion is a magnetic nanostructure which can be used as an information carrier. In this paper, we simulate vortex-free Gaussian wave packet by incorporating spin–orbit coupling (SoC) into three-component Bose–Einstein condensates (BECs). We next observe that skyrmions can be naturally generated from vortex-free Gaussian wave packet, further these structurally asymmetric devices are constructed and initial device classifications are carried out. A spin device consisting of vertically-stacked multiple skyrmions is proposed termed as skyrmion spintronic synapse (SkSS) and skyrmion spintronic Neuron (SkSN). This paper depicts training the neural network with surrogate gradients with deep learning strategies using topologically nontrivial spin textures. The current popular Graphics Processing Unit (GPU)-based neural network computations are compared with the proposed method. This research paves a way for a neuromorphic computing systems on exotic topological solitons.

High Spin Hall Conductivity Induced by Ferromagnet and Interface

AbstractSpin‐orbit‐torque (SOT) offers a highly attractive perspective for manipulating magnetization dynamics in magnetic nanostructures. SOT is been observed and studied in various systems. However, limited by the efficiency, SOT‐induced switching of the ultrahard ferromagnet is still extremely difficult and a further improvement in efficiency is requested. Here, the SOT is reported in chemically disordered soft Fe0.5Pt0.5 and Pt/Fe0.5Pt0.5 bilayers. Due to the magnetization‐strengthened spin Hall effect, the damping‐like torque efficiency and spin Hall conductivity (SHC) in Fe0.5Pt0.5 reach 1.11 and 1.08 × 106 ℏ/2e Ω−1 m−1 respectively, much higher than those in conventional materials. Furthermore, the Pt/Fe0.5Pt0.5 interface enhances SHC to a total of 2.93 × 106 ℏ/2e Ω−1 m−1 due to the interfacial symmetry breaking. This system can be used to partially switch the magnetization of ultra‐hard exchange‐spring system with a switching field of 1T by applying a relatively low current. This finding will push forward the development of SOT devices with ultrahigh‐density and low‐power consumption.

Green synthesis of spinel copper ferrite (CuFe2O4) nanoparticles and their toxicity

Abstract In this study, magnetic spinel copper ferrite (CuFe2O4) nanostructures were eco-friendly synthesized using Nasturtium officinale extract. Physicochemical properties of these nanostructures were determined by transmission electron microscopy, field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), vibrating sample magnetometry, and energy dispersive X-ray mapping analysis. XRD patterns conform to the CuFe2O4 formation. SEM results demonstrated ceramic spinel CuFe2O4 nanostructures with spherical surface morphologies. The cytotoxicity effect of CuFe2O4 nanostructures against rat pheochromocytoma (PC12) cells was evaluated based on MTT assay. The magnetic nanostructures had low toxicity at a concentration of 250 µg/mL. It appears that these nanostructures can be considered as suitable candidates for drug delivery and other biomedical applications, because of their low toxicity effects.

Magnetic force microscopy of an operational spin nano-oscillator

Magnetic force microscopy (MFM) is a powerful technique for studying magnetic microstructures and nanostructures that relies on force detection by a cantilever with a magnetic tip. The detected magnetic tip interactions are used to reconstruct the magnetic structure of the sample surface. Here, we demonstrate a new method using MFM for probing the spatial profile of an operational nanoscale spintronic device, the spin Hall nano-oscillator (SHNO), which generates high-intensity spin wave auto-oscillations enabling novel microwave applications in magnonics and neuromorphic computing. We developed an MFM system by adding a microwave probe station to allow electrical and microwave characterization up to 40 GHz during the MFM process. SHNOs—based on NiFe/Pt bilayers with a specific design compatible with the developed system—were fabricated and scanned using a Co magnetic force microscopy tip with 10 nm spatial MFM resolution, while a DC current sufficient to induce auto-oscillation flowed. Our results show that this developed method provides a promising path for the characterization and nanoscale magnetic field imaging of operational nano-oscillators.

Synthesis of magnetic polypyrrole modified sodium alginate nanocomposite with excellent antibacterial properties and optimization of dye removal performance using RSM

In this study, a novel polypyrrole/Sodium-Alginate/CuFe2O4 magnetic nanostructure (PPy/NA-Alg/CuFe2O4) was synthesized by the hydrothermal route and used as an adsorbent in order to eliminate Direct Blue 199 (DB199) dye from wastewater. The characterization of the synthesized PPy/NA-Alg/CuFe2O4 was confirmed by investigation of SEM, TEM, FTIR, XRD, and VSM analyses. Five significant operational parameters including initial dye concentration (20–100 mg/L), temperature (25–45 °C), the dose of adsorbent (2–22 mg), contact time (10-210 min), and pH (2-10) were optimized to achieve the greatest removal efficiency of DB199 by a central composite rotatable design (CCRD) combined with response surface methodology (RSM). A high coefficient of determination (R2 = 0.99) was calculated by analysis of variance (ANOVA). Under optimal conditions, adsorption dosage = 7.00 mg, temperature = 30.61 °C, initial concentration = 80.00 mg/L, pH = 4.00 and contact time = 159.42 min, the maximum adsorption capacity of the adsorbent (80.36) was highly matched with the predicted response values, illustrating the appropriate of RSM in optimum conditions. The experimental data were matched well to the Langmuir isotherm model and both pseudo-first-order and pseudo-second-order kinetics. Additionally, thermodynamic parameters exhibited spontaneous nature and exothermic reaction. Adsorption–desorption experiments evidenced that the PPy/NA-Alg/CuFe2O4 synthesized could be used for up to three successive adsorption cycles. Furthermore, the nanocomposite showed strong antibacterial activity against two model microorganisms, one gram-negative (Escherichia coli) and one gram-positive (Staphylococcus aureus) via disc diffusion and linear cultivation methods.

Conductive filament nanostructures and their magnetization reversal in NiO resistive switching memory cells

We demonstrate that conductive filament (CF) nanostructures in NiO thin film resistive switching memory (RRAM) cells present unique magnetic properties. The CF nanostructures of nanodots and nanorods formed using a conductive atomic force microscopy tip were fabricated through the forming process of CFs for the NiO RRAM cells. In the current–voltage curve, unipolar resistive switching behavior was observed. The ferromagnetic domain and magnetization switching of CF nanostructures were characterized using magnetic force microscopy. In principle, nanoscale-sized magnetic nanostructures possess superparamagnetism due to their thermal fluctuations. In this study, however, CF nanorods with a length of 30 nm exhibited ferromagnetism because the exchange bias effect occurred at the interface between the antiferromagnetic NiO and the CF nanorod. Therefore, the ferromagnetism of the CF nanostructures is the origin of the magnetization switching and can be favorable in magnetic storage device applications by overcoming the superparamagnetic limits with the exchange bias effect.

A theoretical simulation of the magnetic properties of nanocomposites based on graphene nanoflakes

AbstractUsing exact diagonalization, the density matrix renormalization group approach and the quantum Monte‐Carlo method, we studied the peculiarities of the magnetization profiles and the possibility of spin switching for the Heisenberg spin models of low‐dimensional composite magnets formed by graphene nanoclusters and complex transition‐metal compounds. For these models, we found the presence of intermediate plateaus in the low‐temperature magnetization profiles, which is in agreement with known experimental and theoretical studies of the magnetization profiles of nanostructured magnets with the ferrimagnetic spin ordering in the ground state. For spin‐chain model of composite magnets proposed, we also found a possibility of single and double spin switching with the macroscopic jump of the ground state spin results from frustrated spin interactions.

Enhanced optical mode coherence in exchange coupled soft magnetic multilayers

We report on an all-optical investigation of coupled spin excitation modes in a series of magnetic trilayer structures. Using time-resolved magneto-optic Kerr effect (tr-MOKE) magnetometry, we observe multi-mode coherent spin excitations in Ni81Fe19/Ru/Co49Fe49V2 multilayers even though the tr-MOKE optical detection is sensitive only to the Co49Fe49V2 magnetization dynamics. Frequency shifts of the different modes indicate that the coupling between the Ni81Fe19 and Co49Fe49V2 layers varies from anti-ferromagnetic to ferromagnetic to uncoupled as the Ru spacer layer thickness is increased from 8 Å to 200 Å. The lifetime of the high frequency coherent oscillations in the Co49Fe49V2 layer increases by over 200%–300% even in the case of uncoupled Ni81Fe19 and Co49Fe49V2 layers with a 200 Å thick Ru spacer. The results suggest an additional method to decrease the damping of high-moment alloys in layered magnetic nanostructures.

Cu-mediated grain boundary engineering in Nd–Ce–Fe–B nanostructured permanent magnets

Grain boundary (GB) engineering is of general significance for developing high-performance permanent magnets (PMs), but remains largely lacking in Nd–Ce–Fe–B nanostructured PMs containing the novel REFe2 (1:2, RE = rare earth) phase, previously considered as a coercivity-damaging agglomerated paramagnetic precipitate. Here we present a Cu-mediated GB engineering strategy that delicately controls the composition, distribution and magnetism of the 1:2 phase in (Nd0.5Ce0.5)30.5Fe68.5-xCuxB1.0 nanostructured magnets (x = 0–0.5). Experimental studies show that the incorporated Cu enables the formation of a continuous 1:2 GB phase, which is reported for the first time in Nd–Ce–Fe–B nanostructured magnets. More interestingly, the Cu infiltration into the 1:2 phase also permits more Nd to replace Ce, generating a novel Nd-dominated 1:2 phase with a ferro-paramagnetic transformation. A certain fraction of the 1:2 phase with ferromagnetic nature results in an obvious kink near −35 kA/m reversal field at 300 K, which disappears after the ferro-paramagnetic transition at 350 K. At optimal Cu doping (x = 0.2) with a maximized coercivity of 992 kA/m, the paramagnetic and ferromagnetic 1:2 phases coexist with highest total fraction of 4.8 wt%, revealing an advantageous role of paramagnetic 1:2 GB phase in enhancing coercivity. Our exploration paves a novel Cu-mediated approach for rational engineering of the 1:2 GB phase, which may exert far-reaching significance for developing low-cost Nd–Ce–Fe–B PMs.

Magnetic Biosignatures of Magnetosomal Greigite From Micromagnetic Calculation

AbstractGreigite magnetosomes produced by magnetotactic bacteria (MTB) are widely distributed in natural environments, but large uncertainties remain regarding their magnetic biosignatures. Here, we have constructed micromagnetic models with realistic biogenic greigite particles to quantify the magnetic properties and magnetotaxis efficiency of greigite‐producing MTB cells. Our calculations suggest coercivity (Bc) of ∼15–21 mT for intact greigite‐producing rod‐shaped MTB and many‐celled magnetotactic prokaryotes, with Bc decreasing to ∼11 mT for greigite magnetofossils with clumped particles. These magnetic signatures make biogenic greigite distinguishable from typical biogenic magnetite and inorganic greigite, providing reliable magnetic criteria to detect biogenic greigite in a wide range of environmental and geological settings. Our numerical calculations suggest that rod‐shaped greigite‐producing MTB have a similar magnetotaxis efficiency to magnetite MTB, likely by biomineralizing more greigite crystals to compensate for the lower saturation magnetization of greigite and less ordered chains in greigite MTB cells, demonstrating biological‐controlled optimization of their magnetic nanostructure.

Quercetin loading on mesoporous magnetic MnFe2O4@ hydroxyapatite core-shell nanoparticles for treating cancer cells

Despite the availability of various nanostructure for cancer cells therapeutic, caring hydrophobic drugs to the target site is still one of the great challenges in chemotherapy. In this study, quercetin (QC), a poorly water-soluble natural anticancer agent, was used as a model drug to evaluate the efficiency of mesoporous magnetic MnFe2O4 core-shell nanocomposite particles. A simple co-precipitation method was employed to synthesis MnFe2O4 as core of nanostructure. Then, the obtained MnFe2O4 nanoparticles were coated with mesoporous hydroxyapatite (HA) shell as a new perspective for drug loading. The magnetic mesoporous nanostructure had specific surface area and mean pore size of 165.44 m2/g and 11.561 nm, respectively. In QC loading process, the MnFe2O4@HA nanostructure demonstrated loading capacity of 123 µg/mg with pH-depended release manner. In compare with free QC, loaded QC on MnFe2O4 core-shell nanocomposite particles exhibited 55% higher antioxidant activities against free 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. Moreover, comparative in-vitro anticancer studies on Michigan cancer foundation (MCF)-7 cells, breast cancer cell line, demonstrated more reduction in number of viable cells (35.6%) using loaded QC than that of free QC (50.76%), suggesting improvement in the solubility of QC by loading onto mesoporous magnetic nanocomposite particles compared to free QC.

Tuning quantum heat transport in magnetic nanostructures by spin-phonon interaction

The introduction of spin degree of freedom has not only made the electronic transport properties colorful, but also highly attracted people's attention to the spin-related quantum heat transport, with the rapid progress of spin caloritronics in recent year. Against this background, the modeling and tuning of quantum heat transport in magnetic nanostructures has become an emerging and attractive topic. In particular, the spin-phonon interaction has played a crucial role in the novel transport behaviors of heat and spin. In this perspective article, we give an insight into the current theoretical and experimental progresses and discuss the further research perspectives of spin-phonon interaction-related heat transfer.

CoFe2O4@Methylcellulose/AC as a New, Green, and Eco-friendly Nano-magnetic adsorbent for removal of Reactive Red 198 from aqueous solution

• Methylcellulose (MC) was played an essential role to improve the nanomagnetic adsorbent structure for the Reactive Red 198 (RR198) adsorption. • CoFe 2 O 4 @MC/AC was synthesized as a novel nanomagnetic adsorbent with a facile, simple, and green microwave-assisted coprecipitation method. • The physical and chemical structure of CoFe 2 O 4 @MC/AC were approved with FTIR, FESEM, EDS, Mapping, Line Scan, XRD, VSM, and BET techniques. • The isotherm, kinetic and thermodynamic of RR198 adsorption were investigated. • CoFe 2 O 4 @MC/AC exhibited good chemical stability and reusability. Methylcellulose (MC) is the most common commercial cellulose ether and the most attractive biopolymer due to its cheap cost of biodegradability, biocompatibility, hydrophilicity, and lack of toxicity. In this study, CoFe 2 O 4 @MC/activated carbon (AC) was synthesized as a unique magnetic nano-adsorbent in the presence of MC biopolymer for Reactive Red 198 (RR198) dye removal. The nano-magnetic adsorbent was characterized by FESEM (Field emission scanning electron microscopy), EDS (Energy-dispersive X-ray spectroscopy), Mapping, Linescan, BET (Brunauer–Emmett–Teller), FTIR (Fourier Transform Infrared Spectroscopy), XRD (X-Ray Diffraction), and VSM (Vibrating-Sample magnetometer). For simple separation by external magnetic fields, the Ms value was 57.91 emu/g. According to XRD analysis, the nano-adsorbent maintains its crystal structure, with an average crystal size of 11 nm. The maximum removal efficiencies of RR198 for synthetic and real wastewater samples under optimal conditions (an initial concentration of 10 mg/L, pH 3, contact time of 10 min, nanocomposite dose of 1.5 g/L, and a temperature of 25 °C) were 92.2% and 78%, respectively. The adsorption experiments were fitted well with the Freundlich isotherm (R 2 = 0.989) and pseudo -second-order kinetic (R 2 = 0.995). The values of entropy changes (ΔS = 35.087 kJ/mol.k), enthalpy changes (ΔH = -9.862 kJ/mol), and negative Gibbs free energy changes (ΔG) showed that the adsorption process was exothermic. Finally, the reusability findings showed that after six recovery cycles, the efficiency decreased slightly (90.1%). In the end, it can be concluded that the prepared CoFe 2 O 4 @Methylcellulose/AC can be used as an efficient adsorbent for the removal of RR198 from an aqueous solution.

Synthesis and Characterization of peri‐Heptacene on a Metallic Surface

AbstractThe synthesis of long n‐peri‐acenes (n‐PAs) is challenging as a result of their inherent open‐shell radical character, which arises from the presence of parallel zigzag edges beyond a certain n value. They are considered as π‐electron model systems to study magnetism in graphene nanostructures; being potential candidates in the fabrication of optoelectronic and spintronic devices. Here, we report the on‐surface formation of the largest pristine member of the n‐PA family, i.e. peri‐heptacene (n=7, 7‐PA), obtained on an Au(111) substrate under ultra‐high vacuum conditions. Our high‐resolution scanning tunneling microscopy investigations, complemented by theoretical simulations, provide insight into the chemical structure of this previously elusive compound. In addition, scanning tunneling spectroscopy reveals the antiferromagnetic open‐shell singlet ground state of 7‐PA, exhibiting singlet–triplet spin‐flip inelastic excitations with an effective exchange coupling (Jeff) of 49 meV.

Synthesis and Characterization of peri-Heptacene on a Metallic Surface.

The synthesis of long n-peri-acenes (n-PAs) is challenging as a result of their inherent open-shell radical character, which arises from the presence of parallel zigzag edges beyond a certain n value. They are considered as π-electron model systems to study magnetism in graphene nanostructures; being potential candidates in the fabrication of optoelectronic and spintronic devices. Here, we report the on-surface formation of the largest pristine member of the n-PA family, i.e. peri-heptacene (n=7, 7-PA), obtained on an Au(111) substrate under ultra-high vacuum conditions. Our high-resolution scanning tunneling microscopy investigations, complemented by theoretical simulations, provide insight into the chemical structure of this previously elusive compound. In addition, scanning tunneling spectroscopy reveals the antiferromagnetic open-shell singlet ground state of 7-PA, exhibiting singlet-triplet spin-flip inelastic excitations with an effective exchange coupling (Jeff ) of 49 meV.