Large Saturation Magnetization Research Articles

Enhanced magnetic, antibacterial and optical properties of Sm doped ZnO thin films: Role of Sm doping

Abstract Thin films of Sm3+ ions doped ZnO were prepared by dip coating method. To enhance the oxygen vacancy in the host ZnO lattice and obtain crystallinity, the thin films were annealed at 400 °C for 2 h in air. X-ray diffractions (XRD) study displays the hexagonal wurtzite structure of ZnO with crystallite size in the range of 27.37–24.21 nm. The induced carrier concentration, intrinsic defects and oxygen vacancies produced a blue shift in the band gap (Eg) with an increase in Sm doping percentage. The surface morphology is granular with slight agglomeration. Thin films have shown violet photoluminescence. The emissions intensity can be tailored by increasing the Sm percentage which is due to the increase in defect concentration as well as find application in optoelectronic devices. Room temperature ferromagnetism is recorded in the thin films. Hysteresis show that 1 at. wt. % Sm doped ZnO has larger saturation magnetization than 5 at. wt. % Sm doped thin films. The work has established that rare earth element doping in ZnO produces diluted magnetic semiconductors which can be part of absorber layer of solar cell, to store data in memory devices and optoelectronics applications. Antibacterial studies were conducted for Staphylococcus aureus (S. Aureus), klebsiella pneumonia (K. B), Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli) bacterial strains by applying the agar well diffusion method to suspension containing undoped ZnO and Sm doped ZnO nanoparticles. The enhancement in the zone of inhibition with an increase in samarium exhibits high antibacterial activity. The results predict that Sm doped ZnO is a good possibility of food packing, removal of the tumor, treatment of pneumonia and a diagnosis of malign diseases.

Prediction of large magnetic anisotropy for non-rare-earth based permanent magnet of Fe16 − xMnxN2 alloys

Exploring the metastable magnetic nanostructures of Mn substituted α″-Fe16N2 with large saturation magnetization μ0MS, high Curie temperature TC and giant magnetic anisotropy are of technological merit as promising candidates for non-rare-earth based permanent magnets. Here, we present in-depth analysis for the structural and magnetic properties of Fe16 − xMnxN2 using first-principles calculations. We predict a large magnetocrystalline anisotropy energy (MAE) constant of K1 = 2.02 MJ/m3 for the Fe14Mn2N2 alloy, which is more than twice that of pristine Fe16N2. The underlying mechanism associated with boosting K1 is attributed to the local distortion of orbitals induced by Mn substitution. The MAE is also carefully analyzed in terms of reciprocal space analysis by employing the magnetic force theorem, revealing the regions in the Brillouin zone that are prominent for giving rise to MAE.

Selective and efficient adsorption of anionic dyes by core/shell magnetic MWCNTs nano-hybrid constructed through facial polydopamine tailored graft polymerization: Insight of adsorption mechanism, kinetic, isotherm and thermodynamic study

It is a big challenge to design advanced adsorbents that have high adsorption capacity and excellent selectivity to efficiently remove organic dyes from complex environmental systems. Herein, by utilizing the adhesion property of polydopamine (PDA) and its crosslinking reaction with polyethyleneimine (PEI), a novel core/shell magnetic MWCNTs/Fe3O4@(PDA + PEI) nano-hybrid that carries superior adsorption performance of dyes was constructed through facile polydopamine tailored graft polymerization. In such hierarchical structure, the inner shell of Fe3O4 nanoparticles and outer shell of (PDA + PEI) contributed to the abundant active adsorption sites, large specific surface area (126 m2/g) and high saturation magnetization value (10.91 emu/g). As a result, the prepared adsorbent exhibited highly selective adsorption performance toward multiple anionic dyes, including MB, CR, and MO with maximum adsorption capacity of 1449, 1006, and 935 mg/g at 298.15 K, respectively. It was found that the main adsorption mechanism was attributed to the hydrogen bonding and electrostatic interaction. The kinetics data fitted well with the pseudo-second-order model, and both the Langmuir and Freundlich isotherm models presented well fit to the isotherm data. The investigation of thermodynamic study indicated that the adsorption of anionic dyes onto core/shell magnetic MWCNTs/Fe3O4@(PDA + PEI) nano-hybrid was spontaneous and endothermic. More importantly, the adsorbent presented excellent regeneration property after multiple adsorption-desorption cycles and prominent stability in harsh environments, especially in the alkaline condition. Therefore, these results revealed the promising applications of hierarchical MWCNTs/Fe3O4@(PDA + PEI) nano-hybrid in water remediation.

Magnetic Vortex States in Toroidal Iron Oxide Nanoparticles: Combining Micromagnetics with Tomography.

Iron oxide nanorings have great promise for biomedical applications because of their magnetic vortex state, which endows them with a low remanent magnetization while retaining a large saturation magnetization. Here we use micromagnetic simulations to predict the exact shapes that can sustain magnetic vortices, using a toroidal model geometry with variable diameter, ring thickness, and ring eccentricity. Our model phase diagram is then compared with simulations of experimental geometries obtained by electron tomography. High axial eccentricity and low ring thickness are found to be key factors for forming vortex states and avoiding net-magnetized metastable states. We also find that while defects from a perfect toroidal geometry increase the stray field associated with the vortex state, they can also make the vortex state more energetically accessible. These results constitute an important step toward optimizing the magnetic behavior of toroidal iron oxide nanoparticles.

Itinerant ferromagnetism in van der Waals Fe5−xGeTe2 crystals above room temperature

Two-dimensional (2D) van der Waals (vdW) magnets have recently attracted increasing attention, as they provide a novel system for exploring 2D magnetism. However, intrinsic ferromagnetism in 2D systems has almost exclusively been observed at low temperatures, limiting their technological relevance. ${\mathrm{Fe}}_{\mathrm{N}}{\mathrm{Ge}\mathrm{Te}}_{2}$ ($N=3$, 4, and 5) systems are currently becoming the most attractive 2D vdW materials due to their relatively high Curie temperatures and large saturation magnetization. However, the nature of their complex yet intriguing magnetic behaviors is still unclear, in part due to the multiple inequivalent iron sites and iron vacancies. Here, we show evolution of magnetic ordering transitions in ${\mathrm{Fe}}_{5\ensuremath{-}x}{\mathrm{Ge}\mathrm{Te}}_{2}$ with high Curie temperature and a strong saturation magnetization using photoemission electron microscopy and transport measurements. At 275 K, the ferromagnet transitions to a ferrimagnet, and below 110 K transitions to a state with glassy clusters. These are evidenced from temperature-dependent magnetic stripe domain evolution and anisotropic magnetoresistance measurements. Our findings show a clear magnetic ground state of ${\mathrm{Fe}}_{5\ensuremath{-}x}{\mathrm{Ge}\mathrm{Te}}_{2}$ at room temperature which signals that ${\mathrm{Fe}}_{5\ensuremath{-}x}{\mathrm{Ge}\mathrm{Te}}_{2}$ system is a very promising candidate for spintronic devices and provides a material design pathway to further increase the Curie temperature and saturation moments in vdW ferromagnets.

Micromagnetic study of the write performance in dynamic-double and quad-interface magnetic tunnel junctions

We have studied the thermal stability and switching behavior of the recently proposed dynamic dual (DD-) magnetic tunnel junction (MTJ) with a fixed and a switchable reference layer and quad-interface (Quad-) MTJ with double-stacked free layers using micromagnetic simulation. We found that the upper free layer of the Quad-MTJ acts as a switchable reference layer with a considerably large saturation magnetization (Ms). We also found that both the thermal stability and switching time increase with an increase in the Ms of the switchable reference layer. A detailed understanding of these characteristics is critical in order to use these MTJs as embedded memories.

Modification of magneto-transport and magnetic properties of (1-x) La0.7Sr0.3Mn0.95Co0.05O3 + (x) ZnO composite samples

We have investigated the effect of magneto-transport and magnetic properties of (1-x)La0.7Sr0.3Mn0.95Co0.05O3 (LSMCO)+(x)ZnO (x = 0%, 6%, 9%, 12%, 15% & 18%) composite samples which were synthesized through an inexpensive auto combustion technique. The enhancement of MR was observed over a wide temperature range from low temperature to high temperature which is shown in Fig. 1. Magnetic measurements reveal that the ferromagnetic order of LSMCO is weakened and the magnetic disorder is increased by addition of ZnO content. The Curie temperature (TC1) is almost independent on the ZnO content and is about 347 K for both pure LSMCO and each composite while for only ZnO added LSMCO samples, TC2 was observed and TC2 increases with increase in ZnO content which is shown in Fig. 2. M − H curves that for x = 6% and 9% ZnO added composite samples have large saturation magnetization (MS) as compared to pure LSMCO and remaining composites at all temperatures taken.

Structural, magnetic and dielectric properties of (Li1+, Al3+) co-doped Ni0.5Zn0.5Fe2O4 ferrite ceramics prepared by the sol-gel auto-combustion method

(Li1+, Al3+) co-doped Ni0.5Zn0.5Fe2O4 ferrites, Ni0.5-xZn0.5-xLixAlxFe2O4 (x = 0.000, 0.025, 0.050 and 0.100), were synthesized by the sol-gel auto-combustion method. X-ray diffraction (XRD), field emission scanning electronic microscope (FESEM), vibrating sample magnetometer (VSM) and LCR meter were used to investigate the structural, magnetic and dielectric properties. Results of XRD and SEM indicate that both doping amount and calcination temperature play significant roles in crystal structure and grain growth. Also, it can be observed that the saturation magnetization and the coercivity change in a noticeable manner. The Ni0.475Zn0.475Li0.025Al0.025Fe2O4 ferrite sintered at 1200 °C has a relatively low coercivity value (62.93 Oe) and the largest saturation magnetization (110.95 emu/g). Besides, dielectric behavior is also improved by Li1+ and Al3+ co-doping.

Strain and electric field control of the orbital and spin order in multiferroic $$\hbox {BiMnO}_3$$

The new frontier for spintronics is the realization of devices in which the spin can be controlled by electric fields. Multiferroics, materials exhibiting strong interplay between spin and orbital degrees of freedom, are candidates for the realization of such a paradigm. In this work, we study the magnetoelectric coupling in epitaxial $$\hbox {BiMnO}_3$$ thin films which exhibit a large saturation magnetization. By combining X-ray absorption spectroscopy data and theoretical modeling, we demonstrate that $$\hbox {BiMnO}_3$$ thin films have an improper magnetoelectric behavior, characterized by competing antiferromagnetic and ferromagnetic correlations. As a consequence, we show that in these materials the Mn-3d orbital and magnetic orders can be tuned via the ferroelectric polarization, opening perspectives for the realization of novel spintronic devices.

The buffer layer effect of the exchange stiffness constants on Co thin film

The exchange stiffness of Cobalt thin films with various buffer layers (Pd, Pt, Ta, and no buffer) has been studied by Brillouin scattering in the applied magnetic field of up to 175 mT. We found that Pd and Pt buffer layers led to higher exchange stiffness constants more than 12% compared to the Ta buffer layer, whereas, it was difficult to determine the exchange stiffness constant with no buffer layer due to broad spinwave spectra with poor signal-to-noise ratios. The determined exchange stiffness constant value is 25.7 ± 0.1, 25.6 ± 0.2, and 22.7 ± 0.1 pJ/m for Pd, Pt, and Ta buffer layers. We also observed that the Pd-underlayered sample gives us the largest saturation magnetization and in contrast the Ta underlayer shows the relatively smaller values. This observation indicates that the exchange stiffness constant and the saturation magnetization exhibit the same trend on various buffer layers.

Bending Strain-Tailored Magnetic and Electronic Transport Properties of Reactively Sputtered γ'-Fe4N/Muscovite Epitaxial Heterostructures toward Flexible Spintronics.

The strain modulation on the magnetic and electronic transport properties of the ferromagnetic films is one of the hot topics due to the practical applications in flexible and wearable spintronic devices. However, the large strain-induced saturation magnetization and resistance change is not easy to achieve because most of the ferromagnetic films deposited on flexible substrates are polycrystalline or amorphous. Here, the flexible epitaxial γ'-Fe4N/mica films are fabricated by facing-target reactive sputtering. At a tensile strain with a radius of curvature (ROC) of 3 mm, the saturation magnetization (Ms) of the γ'-Fe4N/mica film is tailored significantly with a maximal variation of 210%. Meanwhile, the magnetic anisotropy was broadly tunable at different strains, where the out-of-plane Mr/Ms at a tensile strain of ROC = 2 mm is six times larger than that at the unbent state. Besides, the strain-tailored longitudinal resistance Rxx and anomalous Hall resistivity ρxy appear where the drop of Rxx (ρxy) reaches 5% (22%) at a tensile strain of ROC = 3 mm. The shift of the nitrogen position in the γ'-Fe4N unit cell at different bending strains plays a key role in the strain-tailored magnetic and electronic transport properties. The flexible epitaxial γ'-Fe4N films have the potential applications in magneto- and electromechanical wearable spintronic devices.

Long-Range Magnetic Order in Oxide Quantum Wells Hosting Two-Dimensional Electron Gases.

To incorporate spintronics functionalities into two-dimensional devices, it is strongly desired to get two-dimensional electron gases (2DEGs) with high spin polarization. Unfortunately, the magnetic characteristics of the typical 2DEG at the LaAlO3/SrTiO3 interface are very weak due to the nonmagnetic character of SrTiO3 and LaAlO3. While most of the previous works focused on perovskite oxides, here, we extended the exploration for magnetic 2DEG beyond the scope of perovskite combinations, composing 2DEG with SrTiO3 and NaCl-structured EuO that owns a large saturation magnetization and a fairly high Curie temperature. We obtained the 2DEGs that show long-range magnetic order and thus unusual behaviors marked by isotropic butterfly shaped magnetoresistance and remarkable anomalous Hall effect. We found evidence for the presence of more conductive domain walls than elsewhere in the oxide layer where the 2DEG resides. More than that, a relation between interfacial magnetism and carrier density is established. On this basis, the intermediate magnetic states between short-range and long-range ordered states can be achieved. The present work provides guidance for the design of high-performance magnetic 2DEGs.

A Novel Type of Magnetic Fe₂O₃/Fe₃O₄ Heterogeneous Microparticles Prepared via the Ethanol-Water Reflux and Rapid Combustion Process.

A novel type of magnetic Fe₂O₃/Fe₃O₄ heterogeneous microparticles with ellipsoidal macropores was prepared via the ethanol-water reflux and rapid combustion process. The experimental results showed that the volume of absolute ethyl alcohol and the calcination temperature were the key factors to the grain sizes and the magnetic properties, the calcination temperature largely affected the saturation magnetization and the grain size of Fe₂O₃/Fe₃O₄ heterogeneous microparticles, and the amount of absolute ethyl alcohol also tremendously affected the saturation magnetization, however, the amount of absolute ethyl alcohol affected little on the grain size. Fe₂O₃/Fe₃O₄ heterogeneous microparticles calcined at 200 °C for 1 h with absolute ethyl alcohol of 20 mL had the largest saturation magnetization of 90.1 Am²/kg.

A facile one-pot method for synthesis of single phase Co2C with magnetic properties

Cobalt carbide nanoparticles including Co2C and Co3C attract great interest as magnetic materials due to their large coercivities and high saturation magnetization. However, it’s hard to obtain the pure phase Co2C with good magnetic properties. A facile method to synthesize the pure phase ferromagnetic Co2C via a one-step polyol reduction process is developed. The crystal structure, morphology and composition of Co2C nanoparticles are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Saturation magnetization and coercivity of the Co2C measured at 300 K are 13.6 emu g−1 and 0.58 kOe, respectively. The carbon contents, particle size and morphology of the Co2C are responsible for the large magnetization and high coercivity. This work will provide a strategy to synthesize pure metal carbides for applications in magnetic fields or energy materials.

Magnetic Properties of Tetragonal Cobalt Manganese Ferrite Particles Prepared Using the Molten Salt Method

Both magnetization and magnetic anisotropy of CoMn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2-x</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> particles composed of the Jahn-Teller (JT) Mn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> and Co <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ions with an expected large magnetoelastic effect were investigated. CoMn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2-x</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> particles were prepared by using a molten salt method with KBr as a fluxing agent. A tetragonally distorted spinel structure was confirmed for x = 1.3 or higher. This suggests that an increase in Mn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> ions causes JT distortion of c/a > 1. However, Mn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> doping causes spin canting and decreased magnetization. A large saturation magnetization of M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> = 44 emu/g and high coercivity of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> = 4300 Oe were observed for the sample with x = 1.4 at 10 K. In addition, the magnetic anisotropy field, H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</sub> , and H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> increased with the increasing x from x = 1.3, where JT distortion was first observed.

Synthesis and Physical Properties of Antiperovskite CuNFe3 Thin Films via Solution Processing for Room Temperature Soft-Magnets

Antiperovskite CuNFe3 (CNF) thin films have been successfully prepared by chemical solution deposition (CSD) for the first time. They are versatile in many applications as an iron-based nitride. The preparation of pure CNF thin films is a challenging work for the complexity of the phase diagram. Herein, the CNF thin films are phase-pure and polycrystalline. Annealing temperature effects on the microstructures and physical properties were investigated, showing that the CNF thin films are metallic and can be considered as a candidate for room temperature soft-magnets with a large saturated magnetization (Ms) and a low coercive field (Hc). At high temperatures, the electrical transport behavior of CNF thin films presents a low temperature coefficient of resistivity (TCR) value, while the electron–electron interaction is prominent at low temperatures. The reported solution methods of CNF thin films will enable extensive fundamental investigation of the microstructures and properties as well as provide an effective route to prepare other antiperovskite transition-metal nitride thin films.

Molten salt synthesis, formation mechanism and greatly enhanced magnetic properties of randomly oriented BaM ferrite

Due to the influence of specific preparation process and product microstructure characteristics, it is a difficult task to prepare the randomly oriented BaFe12O19 (BaM) ferrite with large remanent magnetization (Mr) and high saturation magnetization (Ms), which hinder the practical application of the BaM ferrite. One of the means to solve this problem is to prepare well-developed hexagonal plate-like structure and single magnetic domain particles by lower synthesis temperature. In this study, the BaM ferrite were prepared using molten salt synthesis (MSS) method, and the preparation conditions of excellent magnetic properties and the formation mechanism of BaM ferrite synthesized by molten salt were discussed. Powder X-ray diffraction (PXRD), scanning electron microscope (SEM) and magnetic properties analyses indicated that the BaM ferrite with greatly enhanced magnetic properties could be obtained by adjusting the calcination temperature, Fe3+/Ba2+ molar ratio and the salts to reactants mass ratio R. The Ms and Mr of the prepared BaM ferrite were 71.9 emu/g and 39.5 emu/g, respectively. The Ms of the prepared BaM ferrite was significantly enhanced, and the Mr was much higher than that of BaM ferrite prepared by other methods. Using hydrothermal method synthesized spindle-like α-Fe2O3 as a raw material confirmed that the formation mechanism of molten salt synthesis of BaM ferrite was dissolution and precipitation mechanism. The formation of BaM ferrite underwent a series of processes including BaFe2O4 and BaFe4O7 formation, iron oxide dissolution, BaFe2O4 and BaFe4O7 desolvation of Ba2+, ion diffusion, nucleation growth and precipitation.

The effects of oxygen pressure on the structural, magnetic, and ferroelectric properties of 0.55BiFe0.95Ga0.03Mn0.02O3–0.45BaTiO3 thin films

0.55BiFe0.95Ga0.03Mn0.02O3–0.45BaTiO3 (BFGMO–BTO) thin films have been epitaxially grown on (0 0 1)-oriented Nb-doped SrTiO3 (NSTO) single-crystal substrates by the pulsed laser deposition. X-ray diffraction, selected area electron diffraction, magnetic hysteresis loop, and piezoresponse force microscopy results show that the structural and magnetic properties of the BFGMO–BTO epitaxial films can be progressively tuned by the oxygen pressure (PO2) during film deposition. The films prepared atPO2 = 5 Pa phase separated into BFGMO and BTO phases, however, with increasing PO2 to 20 Pa the films evolve from two phases to single phase with the best crystalline quality, largest saturation magnetization, lowest coercive field and relatively easy-switchable ferroelectric domains.

Study on magnetoelectric properties of Ni0.5Zn0.5Fe2O4/Ba0.8Sr0.2TiO3 composite ceramics based on Bi2O3 as combustion aid

Ni0.5Zn0.5Fe2O4/Ba0.8Sr0.2TiO3 (NZFO/BST) composite ceramics with different additions of Bi2O3 (0%, 1%, 3%, and 5% wt) were synthesized via the solid-phase sintering method. XRD analysis indicates that the composite ceramics show bi-phase structure, without apparent secondly phases can be observed. SEM images show that all the specimens have relative dense structure, the grain size is in the range 1–2 μm. A certain amount of Bi2O3 is beneficial to grain growth, the average grain size of NZFO/BST ceramics increases from 179 to 297 nm when the concentration of Bi2O3 is 0 and 3%, respectively. EDS results indicate that the distribution of NZFO phase and BST phase is not uniform. The sample NZFO/BST-3%Bi2O3 not only has the largest dielectric constant (er) in the whole temperature range (25–500 °C), but also presents the smallest dielectric loss (tanδ) at high temperature region (> 400 °C), and the maximum tanδ value is less than 0.4 for all the samples, indicating excellent dielectric performance. Compared with other samples, the specimen NZFO/BST-3%Bi2O3 has the largest remnant polarization (~ 1.14 μC/cm2). The sample NZFO/BST-3%Bi2O3 has the largest leakage current density, while the ceramic NZFO/BST-5%Bi2O3 presents the opposite behavior, the value of leakage current of the sample NZFO/BST-3%Bi2O3 is about 7 times larger than that of the specimen NZFO/BST-5%Bi2O. All the composite ceramics show soft magnetic behavior, since Bi2O3 is a non-magnetic phase, addition of Bi2O3 will dilute the magnetic moment per unit volume so as to decrease the magnetic properties of the ceramics. The sample NZFO/BST-3%Bi2O3 has the second largest saturation magnetization (Mr) of 11.27 emu/g and the smallest coercive field (HC) ~ 3.54 Oe. All the samples show strong magnetoelectric coupling effect, the highest magnetoelectric coupling coefficient is ~ 47 Vcm−1Oe−1, which was obtained in the sample without addition of Bi2O3. In short, the addition of Bi2O3 not only affects the structure of composite ceramics, but also plays an important role in affecting the magnetoelectric performance.

Permanent magnet design assisted by antiferromagnet-ferromagnet interface coupling: A Monte Carlo study

In the pursuit of rare-earth-free permanent magnets, materials with large saturation magnetization (Ms) stand out. However, large Ms results in low anisotropy field, thus additional source of coercivity is needed to make useful magnets for a broad range of applications. In this paper, we investigate the use of interface coupling to an antiferromagnet (AFM) as a means to increase coercivity for permanent magnet design. Results on the effects of Néel temperature, AFM anisotropy, interface coupling strength, AFM volume ratio, as well as temperature dependence are obtained using Monte Carlo (MC) simulations. And before that, we clarify some practices in MC simulations of magnetic hysteresis. The origin of coercivity enhancement is investigated by examining the magnetization reversal process, which is found to agree with well-established theory of exchange bias. Finally, discussions and design suggestions are made on the AFM materials, the geometry, and experimental realization.