Ferromagnetic Exchange Interactions Research Articles

Large magnetocaloric refrigeration performance near room temperature in monolayer transition metal dihalides

Magnetocaloric effect (MCE) exhibits highly efficient and ecological cooling abilities for solid-state refrigeration in contrast to traditional vapor-compression refrigeration. Successive emerging two-dimensional (2D) magnetic materials provide a fertile platform for exploring low-dimensional MCE systems. Here, we focus on a series of 2D transition metal dihalides MX2 (M = Fe, Ru, Os; X = Cl, Br) to explore the maximum isothermal magnetic entropy change (−ΔSmagmax) and adiabatic temperature change (ΔTadmax) under external magnetic field. It is found that FeCl2, FeBr2, and RuCl2 have intrinsically sizable −ΔSmagmax, ΔTadmax, and high thermal conductivity near room temperature, demonstrating superior comprehensive refrigeration performance in comparison with other 2D magnets. It is revealed that strong nearest-neighbor ferromagnetic exchange interaction plays a decisive role in −ΔSmagmax, and the high lattice thermal conductivities of FeCl2 and RuCl2 are attributed to the longer phonon lifetime and larger group velocity of low-frequency acoustic branch. Moreover, moderate strain and carriers doping are able to effectively regulate Curie temperature and magnetocrystalline anisotropy energy and correspondingly enhance −ΔSmagmax. The present work provides important insights for the exploration of 2D magnets for magnetocaloric refrigeration near room temperature.

Effect of Ferromagnetic Exchange Interaction and Crystalline Anisotropy on a Double-Cubic Spin-½ Spin-1 Ising System with a Free Surface

In this study, we employ Monte Carlo simulations to explore the magnetic characteristics of a double-cubic spin-½ and spin-1 ferromagnetic Ising superlattice system, focusing on the impact of surface exchange coupling, anisotropy, and layer thickness. We implemented free boundary conditions along the dimension with an exposed surface. Our findings illuminate the key role played by surface exchange coupling (JAS), which significantly influences the critical temperature (Tc), underscoring its ability to strengthen ferromagnetic interactions within the system. In contrast, the compensation temperature (Tcomp) exhibits relative stability. Furthermore, we unveil the crucial influence of crystalline anisotropy on Tcomp, with higher anisotropy values leading to its augmentation, while Tc remains unaffected. Moreover, when the number of layers is increased from 11 to 21, a marked rise in Tc is observed, accompanied by a minor increment in Tcomp, particularly evident under negative anisotropy conditions.

Bimetallic Ba(II)-Cr(III) and trimetallic Ba(II)-Ln(III)-Cr(III) (Ln(III) = Gd, Tb, Dy, Ho, Er, Yb, Y) coordination polymers formed by Cr(III)-containing building blocks with cyclopropane-1,1-dicarboxylate anions

The reaction of chromium(III) nitrate with Ba(cpdc) (H2cpdc = cyclopropane-1,1-dicarboxylic acid) in a ratio of 1:3 yielded a 1D coordination polymer {[Ba2Cr2(OH)2(cpdc)4(H2O)8]·5H2O}n (1) formed by binuclear units [Cr2(OH)2(cpdc)4]4− and a 3D polymer [Ba2Cr(cpdc)3(NO3)(H2O)6]n (2) constructed from tris-chelate blocks [Cr(cpdc)3]3−. The addition of rare-earth metal nitrates (Cr:Ln = 1:2) in this reaction led to the formation of a series of trimetallic 3D coordination polymers {[Ba3Ln2Cr4(cpdc)12(H2O)24]·8H2O}n (3Ln, Ln = Gd, Tb, Dy, Ho, Er, Yb, Y), in whose structures tris-chelate fragments [Cr(cpdc)3]3− are bound in layers by Ln3+ ions and, further, in a framework due to the coordination of Ba2+ ions. The crystal structures of 1, 2, and 3Gd were determined by single-crystal X-ray diffraction (XRD), and isostructurality of all the compounds in the series 3Ln was proved by powder X-ray diffraction (PXRD). DC-magnetic susceptibility measurements revealed weak ferromagnetic exchange interactions between Cr3+ ions in compound 1 (J = +0.74 cm−1). According to ac-magnetic susceptibility measurements, complexes 3Er and 3Y exhibit field-induced slow relaxation of magnetization. According to the data of simultaneous thermal analysis (STA) and differential scanning calorimetry (DSC) performed under Ar atmosphere, dehydration of the compounds obtained takes place in one (for 1 and 3Gd) or three stages (for 2). The initial temperature of the organic part degradation process decreases when moving from compound 1 containing dimerized bis-chelate fragments [Cr2(OH)2(cpdc)4]4− (330 °C) to compounds 2 (276 °C) and 3Gd (261 °C) based on tris-chelate units [Cr(cpdc)3]3−.

Ferromagnetically Coupled Chromium(III) Dimer Shows Luminescence and Sensitizes Photon Upconversion.

There has been much progress on mononuclear chromium(III) complexes featuring luminescence and photoredox activity, but dinuclear chromium(III) complexes have remained underexplored in these contexts until now. We identified a tridentate chelate ligand able to accommodate both meridional and facial coordination of chromium(III), to either access a mono- or a dinuclear chromium(III) complex depending on reaction conditions. This chelate ligand causes tetragonally distorted primary coordination spheres around chromium(III) in both complexes, entailing comparatively short excited-state lifetimes in the range of 400 to 800 ns in solution at room temperature and making photoluminescence essentially oxygen insensitive. The two chromium(III) ions in the dimer experience ferromagnetic exchange interactions that result in a high spin (S=3) ground state with a coupling constant of +9.3 cm-1. Photoinduced energy transfer from the luminescent ferromagnetically coupled dimer to an anthracene derivative results in sensitized triplet-triplet annihilation upconversion. Based on these proof-of-principle studies, dinuclear chromium(III) complexes seem attractive for the development of fundamentally new types of photophysics and photochemistry enabled by magnetic exchange interactions.

Enhancing ferromagnetism in the Sm(Co, Mn)5 system: Impact on phase stability and magnetic properties

This work demonstrates that Mn can be a beneficial candidate for the performance modulation of permanent magnetic materials like SmCo5. Theoretical calculations reveal that Mn has a large positive contribution to the magnetization of SmCo5, owing to the strong ferromagnetic exchange interaction between Co and Mn atoms. It is also found that Mn could occupy both 2c and 3g crystal sites because of the minute energy difference between them can be easily overcome through thermal activation. Co atoms on the same site with Mn have increasing moments with the increase in Mn content, whereas those on the other sites show decreasing moments. The experimental substitution of Mn for Co leads to a contraction of the SmCo5 single-phase region, and thus pure Sm(Co, Mn)5 phase could only be obtained through subtle control of Sm content by annealing. Significantly, a 13 % increase in saturation magnetization of SmCo5 is achieved through Mn substitution. A slight rise in the Curie temperature is also obtained, suggesting that Mn substitution does not strongly disturb the exchange interactions of the Co sublattice. This study offers a new option for enhancing magnetic properties in Sm–Co systems and introduces novel physical phenomena resulting from Mn substitution, which is worthy of further investigation.

Investigation of structural phase stability, modified magnetic spin order and low temperature spin glass-like phase transitions in Sc-doped M-type BaFe12O19 hexaferrite

This work used two approaches of mechanical alloying before high temperature solid state reaction to synthesize BaFe12-xScxO19 (x = 0.5 to 6.0) system. Rietveld refinement of X-ray diffraction patterns showed the formation of extra phases at higher Sc doping, along with the main magnetoplumbite structure. Raman spectroscopy suggested random distribution of Sc ions at the Fe-sites of hexaferrite structure. X-ray photoelectron spectroscopy (XPS) confirmed the +3 charge state at the Fe/Sc-sites. The Fe 3s band suggested dilution of ferromagnetic 3s-3d spin exchange interactions. The neutron diffraction study re-confirmed random occupancy of the non-magnetic Sc3+ ions at Fe3+ sites of the Sc doped Ba hexaferrite system. The transformation of magnetic spin order from collinear to non-collinear state has shown spin glass-like features at low temperature regime in the dc magnetization curves. This is an effect of dilution of Fe–O–Fe ferrimagnetic super exchange interactions and spin frustration in Sc-doped samples.

Controllable magnetic ground states in metal diiodide MI2 (M: Fe, Co, and Ni) monolayers by electric field

We investigated the controllable magnetic ground states of 1T metal diiodide MI2 (M: Fe, Co, and Ni) monolayers by applying the electric field. To do so, we utilized the generalized Bloch theorem within the density functional theory on the primitive unit cell to examine the appearance of three possible magnetic ground states, namely, ferromagnetic, spiral, and antiferromagnetic states from the specified spiral vector. We found that the ground state can be changed as the electric field increases but depends on the lattice parameter. In general, the spiral ground state exists as the electric field is taken into account, thus all these materials are prominent as multiferroics. Also, based on the competition between ferromagnetic and antiferromagnetic exchange interactions, we observed that for FeI2, the transition from the ferromagnetic exchange to the antiferromagnetic exchange happens as the electric field increases, while CoI2 and NiI2 tend to preserve their original exchange interaction. This implies that only the magnetic state in FeI2 sensitively depends on the electric field.

Correlation between structural – Optical – Magnetic properties of cobalt based double perovskite, Sr2TiCo1-yO6-δ

The influence of charge disorders, non-stoichiometry and oxygen vacancy on the physical properties such as optical properties and magnetic properties of Sr2TiCo1-yO6-δ exhibiting simple cubic (space group Pm-3m) structure has been investigated in the article. An analysis of energy dispersive X-ray spectrum reveals a deficiency of cobalt ions. Variable range hopping conduction mechanism is observed below 100 K. X-ray photoelectron spectroscopy results indicated the presence of oxygen deficiency accompanied by multiple valent cobalt ions (Co4+ and Co3+) in the material. The optical features of the material are noteworthy, with a wide range of significant optical absorption occurring in the UV range, characterized by a band gap of ∼3.03 eV. In addition, huge photoluminescence emission in the visible range and at room temperature was observed. In this context, Sr2TiCo1-yO6-δ is a potential material for optical applications due to its high thermal stability with respect to temperature in air environment. Magnetic studies indicate the presence of mixed exchange magnetic interactions among the cobalt ions with different valence states generated during the synthesis. The weak ferromagnetic exchange interactions involved Co3+-O-Co4+ ions.

Gas-Liquid Interface Route to Hybrid Copper Bromine Perovskite Single-Crystal Membrane with Dielectric Transitions and Ferromagnetic Exchanges.

Single-crystal membranes (SCMs) show great promise in the fields of sensors, light-emitting diodes, and photodetection. However, the growth of a large-area single-crystal membranes is challenging. We report a new organic-inorganic SCMs [HCMA]2CuBr4 (HCMA = cyclohexanemethylamine) crystallized at the gas-liquid interface. It also has low-temperature ferromagnetic order, high-temperature dielectric anomalies, and narrow band gap indirect semiconductor properties. Specifically, the reversible phase transition of the compound occurs at 350/341 K on cooling/heating and exhibits dielectric anomalies and stable switching performance near the phase transition temperature. The ferromagnetic exchange interaction in the inorganic octahedra and the organic layer enables ferromagnetic ordering at low-temperature 10 K. Finally, the single crystal exhibits an indirect semiconducting property with a narrow band gap of 0.99 eV. Such rich multichannel physical properties make it a potential application in photodetection, information storage and sensors.

Colossal Magnetoresistive Switching Induced by d0 Ferromagnetism of MgO in a Semiconductor Nanochannel Device with Ferromagnetic Fe/MgO Electrodes.

Exploring potential spintronic functionalities in resistive switching (RS) devices is of great interest for creating new applications, such as multifunctional resistive random-access memory and novel neuromorphic computing devices. In particular, the importance of the spin-triplet state of cation vacancies in oxide materials, which is induced by localized and strong O-2p on-site Coulomb interactions, in RS devices has been overlooked. d0 ferromagnetism sometimes appears due to the spin-triplet state and ferromagnetic Zener's double exchange interactions between cation vacancies, which are occasionally strong enough to make nonmagnetic oxides ferromagnetic. Here, for the first time, anomalous and colossal magneto-RS (CMRS) with very high magnetic field dependence is demonstrated by utilizing an unconventional RS device composed of a Ge nanochannel with all-epitaxial single-crystalline Fe/MgO electrodes. The device shows colossal and unusual behavior as the threshold voltage and ON/OFF ratio strongly depend on a magnetic field, which is controllable with an applied voltage. This new phenomenon is attributed to the formation of d0 -ferromagnetic filaments by attractive Mg vacancies due to the spin-triplet states with ferromagnetic double exchange interactions and the ferromagnetic proximity effect of Fe on MgO. The findings will allow the development of energy-efficient CMRS devices with multifield susceptibility.

Critical state-induced emergence of superior magnetic performances in an iron-based amorphous soft magnetic composite

Soft magnetic composites (SMCs) play a pivotal role in the development of high-frequency, miniaturization and complex forming of modern electronics. However, they usually suffer from a trade-off between high magnetization and good magnetic softness (high permeability and low core loss). In this work, utilizing the order modulation strategy, a critical state in a FeSiBCCr amorphous soft magnetic composite (ASMC), consisting of massive crystal-like orders (CLOs, ∼1 nm in size) with the feature of α-Fe, is designed. This critical-state structure endows the amorphous powder with the enhanced ferromagnetic exchange interactions and the optimized magnetic domains with uniform orientation and fewer micro-vortex dots. Superior comprehensive soft magnetic properties at high frequency emerge in the ASMC, such as a high saturation magnetization (M s) of 170 emu g−1 and effective permeability (μ e) of 65 combined with a core loss (P cv) as low as 70 mW cm−3 (0.01 T, 1 MHz). This study provides a new strategy for the development of high-frequency ASMCs, possessing suitable comprehensive soft magnetic performance to match the requirements of the modern magnetic devices used in the third-generation semiconductors and new energy fields.

Strong Anisotropic Order Parameters at All-Nitride Ferromagnet/Superconductor Interfaces

Proximity effects between superconductors and ferromagnets (SC/FM) hold paramount importance in comprehending the spin competition transpiring at their interfaces. This competition arises from the interplay between Cooper pairs and ferromagnetic exchange interactions. The proximity effects between transition metal nitrides (TMNs) are scarcely investigated due to the formidable challenges of fabricating high-quality SC/FM interfaces. We fabricated heterostructures comprising SC titanium nitride (TiN) and FM iron nitride (Fe3N) with precise chemical compositions and atomically well-defined interfaces. The magnetoresistance of Fe3N/TiN heterostructures shows a distinct magnetic anisotropy and strongly depends on the external perturbations. Moreover, the superconducting transition temperature T C and critical field of TiN experience notable suppression when proximity to Fe3N. We observe the intriguing competition of interfacial spin orientations near T C (∼ 1.25 K). These findings not only add a new materials system for investigating the interplay between superconductor and ferromagnets, but also potentially provide a building block for future research endeavors and applications in the realms of superconducting spintronic devices.

Cationic mismatch effect on structural and magnetic behavior of La0.5-xEuxCa0.5-yBayMnO3 charge-ordered manganites

In this research, we have tried to investigate the effect of the cationic disorder on charge ordering and magnetic phase separation in La0.5-xEuxCa0.5-yBayMnO3 (x = 0, 0.05, and 0.1) compounds synthesized by using the sol-gel method. All the samples possess the same average ionic radius at A site <rA> and the same Mn3+/Mn4+ ratio. Our analysis confirmed the chemical composition by energy dispersive X-ray spectroscopy and verified the structural integrity and purity of the phase by X-ray diffraction, revealing an orthorhombic structure with Pnma space group, which is in agreement with the tolerance factor. The important mismatch effect observed in the substituted specimens induces drastic effects on the structural and microstructural properties. Magnetic measurements indicate a great reduction of Curie temperature for substituted samples (from 250 K for x = 0 to 90 K for x = 0.05 and 85 K for x = 0.1), which indicates a weakening of ferromagnetic double exchange interactions induced by cationic disorder. The Arrott plots and the magnetocaloric study of the Eu−based samples indicate the persistence of the antiferromagnetic charge-ordered state characterizing the pristine compound (x = 0) as well as the presence of a first-ordered metamagnetic transition for all the studied samples, which is ascribed to the presence of antiferromagnetic domains. Such transition induced the appearance of a shoulder peak near 100 K in the magnetic entropy change curves for high magnetic field values, resulting in an extra cooling efficiency.

Solvent-controlled solid-state phase transitions of a heterospin Cu(II) complex with imidazolyl-substituted nitronyl nitroxide.

Spontaneous solvent-controlled solid-state transformations were observed for a series of polymeric chain solvates [Cu(hfac)2LPr]·0.5Solv (Solv = (CH3)2CO, THF, CH2Cl2, CH2Br2, CHCl3) with 2-(1-propyl-1H-imidazol-5-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (LPr) under ambient conditions. The conversion of powdered polymeric chain [Cu(hfac)2LPr]·0.5THF and [Cu(hfac)2LPr]·0.5(CH3)2CO complexes, accompanied by the loss of solvent molecules, occurs completely to binuclear [Cu(hfac)2LPr]2 within a day. On the other hand, in the case of [Cu(hfac)2LPr]·0.5Solv (Solv = CH2Cl2, CH2Br2, CHCl3), the partial transformation into a desolvated 1D polymer [Cu(hfac)2LPr] or its mixture with [Cu(hfac)2LPr]2 takes much longer time. The magnetic behavior of the isostructural solvates is highly sensitive to the included solvent molecules. The complexes with THF, CH2Cl2, CH2Br2, and CHCl3 undergo a transition to a magnetically ordered state below 4 K, a phenomenon reported for the first time for the polymeric chain Cu(II) complexes with a "head-to-tail" motif. [Cu(hfac)2LPr]·0.5THF and [Cu(hfac)2LPr]·0.5(CH3)2CO undergo a spin transition at 190 K, which is induced by the transformation of the Cu atom environment. In the case of the THF solvate, the increase in the distances between the Cu and oxygen atoms leads to enhanced ferromagnetic exchange interactions, while in the acetone solvate, the nitroxide coordination type changes from axial to equatorial at certain coordination sites, resulting in the emergence of strong antiferromagnetic exchange.

Synthesis and photoinduced behavior of DPP-anchored nitronyl nitroxides: a multifaceted approach.

Understanding and controlling spin dynamics in organic dyes is of significant scientific and technological interest. The investigation of 2,5-dihydropyrrolo[4,3-c]pyrrolo-1,4-dione derivatives (DPPs), one of the most widely used dyes in many fields, has so far been limited to closed-shell molecules. We present a comprehensive joint experimental and computational study of DPP derivatives covalently linked to two nitronyl nitroxide radicals (DPPTh-NN2). Synthesis, single crystal X-ray diffraction study, photophysical properties, magnetic properties established using steady-state and pulse EPR, fast spin dynamics, and computational modelling using density functional theory and ab initio methods of electronic structure and spectroscopic properties of DPPTh-NN2 are presented. The single-crystal X-ray diffraction analysis of DPPTh-NN2 and computational modeling of its electronic structure suggest that effective conjugation along the backbone leads to noticeable spin-polarization transfer. Calculations using ab initio methods predict a weak exchange interaction of radical centers through a singlet ground state of DPPTh with a small singlet-triplet splitting (ΔEST) of about 25 cm-1 (∼0.07 kcal mol-1). In turn, a strong ferromagnetic exchange interaction between the triplet state of DPPTh chromophore and nitronyl nitroxides (with J ∼ 250 cm-1) was predicted.

Crystal structure and magnetic properties ferrites Ba-Fe-O, Bi-Fe-O, synthesized in NGO “Physics-Sun”

Alloys based on Ba-Fe-O have been synthesized in a large solar furnace NGO “Physics-Sun”. The obtained barium hex ferrite with magnetic characteristics suitable for solving technical problems for the manufacture of protective coatings. The experimentally observed increase in the specific magnetization of BiFe0.75Ni0.25O3 with respect to the data obtained in nominally pure bismuth ferrite is associated both with the suppression of the cycloidal spin structure due to the partial substitution of nickel cations for iron cations and with the establishment of ferromagnetic exchange interaction between neighboring Fe3+ and Ni3+ ions. The results of ab initio (LSDA + U approximation of the DFT method) calculations of the band structure suggest that in the ground state BiFe0.75Ni0.25O3 is a semiconductor with a band gap of 1.94 eV.

X-ray absorption near-edge, terahertz and Raman spectroscopies evidence growth-orientation dependent cation order, phase transitions and spin–phonon coupling in half-metallic Ca2FeMoO6 thin films

The disorder due to anti-site cation distribution is intrinsic to the double perovskites wherein the crystal orientations of the substrate template are predicted to offer different degrees of cation order in thin film form. To demonstrate this effect, epitaxial thin films of half-metallic double perovskite Ca2FeMoO6 (CFMO) were prepared on (100) and (111) oriented LaAlO3 substrates in vacuum and nitrogen atmospheres. The findings using X-ray absorption near-edge structure, Terahertz (THz) and Raman spectroscopies, in combination with magnetization show that (111) epitaxial template effectively restricts the Fe–Mo anti-site cation disorder. A resultantly enhanced cation order in (111) films induces dramatic transformations in its properties as follows: (i) significantly enhanced ferromagnetic exchange interactions and saturation magnetization, (ii) a significant increase in the Curie temperatures, (iii) a metallic behavior down to much lower temperature (∼75 K) compared to that down to 200 K for (100) film, (iv) an enhanced spin–phonon coupling. The complex THz optical conductivity spectra evaluated in the framework of Drude and Drude–Smith phenomenological models and the temperature-dependent Raman data fitted to the Balkanski model corroborate well to indicate an enhanced cation order in (111) films. While this study establishes a dominant role of crystallographic orientation in the much-desired control of cation order in double perovskites, a demonstration of the same in room temperature half-metallic CFMO system could reinforce its technological utility both as active and passive components in emergent spintronic functionalities.

Ferromagnetic L12‐Pt3Co Nanowires with Spin‐Polarized Orbitals for Fast and Selective Oxygen Reduction Electrocatalysis

AbstractMagnetic alloys are key to develop efficient catalysts for oxygen reduction reaction (ORR) in fuel cells. During the last decade, it has been shown that spin manipulation of magnetic materials can improve the kinetics of triplet state 3O2 electrocatalysis, promoting the unification between the physics of strongly correlated materials and heterogeneous catalysis. In this study, structurally ordered Pt3Co nanowires (NWs) are synthesized, and their ORR catalytic performances are studied in detail. These intermetallic ordered L12‐Pt3Co NWs exhibit stronger ferromagnetism, superior ORR catalytic activity, and higher tolerance to carbon monoxide than related disordered A1‐Pt3Co NWs, and commercial Pt/C catalyst. These characteristics make them one of (if not) the best catalyst reported nowadays. Density functional theory calculations prove that the L12‐Pt3Co(111) surface displays a lower activation barrier at the ORR rate‐limiting step and better selectivity H2O2/H2O (i.e., lower production of H2O2) compared with disordered A1‐Pt3Co(111). ORR reactivity increases with the level of Co order in the slab. Moreover, L12‐Pt3Co(111) displays more favorable thermodynamics, decreasing the adsorption enthalpies of 3O2, and lower ORR rate‐limiting step, due to ferromagnetic quantum spin exchange interactions (QSEI), compared with Pt(111).

Investigation of conventional exchange bias in (Nd1-xHox)2CoMnO6 (x = 0.0–0.4) double perovskite

In this article, we have investigated the characteristics related to structure, magnetism and exchange bias behavior in single phased polycrystalline samples of (Nd1-xHox)2CoMnO6 (x = 0.0–0.4) (NHCMO) series. The samples were prepared using the conventional solid state reaction technique and they crystalize in monoclinic structure with P21/n space group. The x = 0.0 sample shows the ferromagnetic transitions at TC1 = 139K and TC2 = 170K. These values decrease to 136K and 160K respectively for x = 0.1 sample. However, for other Ho substituted samples we observed only one transition. For x = 0.2, TC is 129K which decreases to 118K for x = 0.4 sample. The ferromagnetic super exchange interaction that arises within the network of Co2+ and Mn4+ ions bridged by O2− ions is the reason of occurring of these transitions. The presence of anti-site defects with antiferromagnetic interactions and subsequent formation of anti-phase boundaries within the system cannot be ignored. To gain a deeper insight into the underlying magnetic interactions, the M − T plots, under both the ZFC and FC conditions, were measured by applying different external magnetic fields. Saturation magnetization (MS) value of 3.68 μB/f.u. is observed in parent sample. The MS value increases to 7.22 μB/f.u. for x = 0.4 sample. Such mixed magnetic ground state of the samples motivates us to perform the exchange bias field measurement revealing an exchange bias field of 725Oe is found for x = 0.0 sample at 5K.

Possible Topological Hall Effect in a Spin Gapless Semiconducting Mn2CoAl Heusler Compound

Topological Hall effect (THE), induced by the interaction of charge carriers with mesoscopic or microscopic noncoplanar spin structures, holds promising applications in the field of spintronics. In the present study, a giant THE of about 2 μΩ cm at room temperature is reported in a bulk spin gapless semiconducting Mn2CoAl cubic Heusler compound. Temperature‐dependent investigation of magneto‐transport data reveals that the Mn2CoAl has the large THE over a wide temperature range of 2–300 K. The alternating current (AC) susceptibility as a function of magnetic field exhibits a smooth and continuous response rather than any kink or anomaly, suggests that the observed THE in the Mn2CoAl compound results from the interaction of charge carriers with the microscopic noncoplanar spin texture. The observed THE as a function of temperature follows the same behavior as the magnetocrystalline anisotropy (MCA) of the cubic Mn2CoAl, indicating the competition of the MCA with ferromagnetic and antiferromagnetic exchange interactions as the origin of the noncoplanar spin texture and hence THE. Micromagnetic simulations further support the emergence of noncoplanar spin structure as a result of the competition between different energies.