Antiferromagnetic Manganese Research Articles

Monolayer MnX and Janus XMnY ( X,Y=S , Se, Te): A family of two-dimensional antiferromagnetic semiconductors

We present first-principles results on the structural, electronic, and magnetic properties of a new family of two-dimensional antiferromagnetic (AFM) manganese chalcogenides, namely monolayer MnX and Janus XMnY (X, Y= S, Se, Te), among which monolayer MnSe was recently synthesized in experiments [\href{https://pubs.acs.org/doi/abs/10.1021/acsnano.1c05532}{ACS Nano 15 (8),13794 (2021)}]. By carrying out calculations of the phonon dispersion and \textit{ab-initio} molecular dynamics simulations, we first confirmed that these systems, characterized by an unconventional strongly coupled bilayer atomic structure (consisting of Mn atoms buckled to chalcogens forming top and bottom ferromagnetic (FM) planes with antiparallel spin orientation) are dynamically and thermally stable. The analysis of the the magnetic properties shows that these materials have robust AFM order, retaining a much lower energy than the FM state even for under strain. Our electronic structure calculations reveal that pristine MnX and their Janus counterparts are indirect-gap semiconductors, covering a wide energy range and displaying tunable band gaps by the application of biaxial tensile and compressive strain. Interestingly, owing to the absence of inversion and time-reversal symmetry, and the presence of an asymmetrical potential in the out-of-plane direction, Janus XMnY become spin-split gapped systems, presenting a rich physics yet to be explored. Our findings provide novel insights in this physics, and highlight the potential for these two-dimensional manganese chalcogenides in AFM spintronics.

Thermoelectric, Magnetic, and Mechanical Characteristics of Antiferromagnetic Manganese Telluride Reinforced with Graphene Nanoplates

Mechanical and thermal stability are the two challenging aspects of thermoelectric compounds and modules. Microcrack formation during material synthesis and mechanical failure under thermo‐mechanical loading is commonly observed in thermoelectric materials made from brittle semiconductors. Herein, the results of graphene‐nanoplates (GNPs) reinforcement on the mechanical and thermoelectric properties of MnTe compound are reported. The binary antiferromagnetic MnTe shown promising thermoelectric characteristics due to the paramagnon–hole drag above the Néel temperature. In this study, different bulk MnTe samples are synthesized with the addition of GNPs in a small quantity (0.25–1 wt%) by powder metallurgy and spark plasma sintering. The thermoelectric factors, magnetic behavior, microstructure, and mechanical properties of the samples are evaluated and analyzed. Nearly 33% improvement is observed in the fracture toughness of MnTe reinforced with 0.25 wt% GNPs compared to the pristine structure. The Néel temperature remains approximately unaffected with the GNP inclusion; however, the low‐temperature ferromagnetic phase impurity is significantly suppressed. The thermal conductivity and power factor decrease almost equally by ≈34% at 600 K; hence, the thermoelectric figure‐of‐merit is not affected by GNP reinforcement in the optimized sample.

Magnetostrictive iron gallium thin films grown onto antiferromagnetic manganese nitride: Structure and magnetism

We report structural and magnetic properties of magnetostrictive Fe100−xGax (x ≈ 15) alloys when deposited onto antiferromagnetic manganese nitride and non-magnetic magnesium oxide substrates. From X-ray diffraction measurements, we find that the FeGa films are single crystalline. Scanning tunneling microscopy imaging reveals that the surface morphologies are dictated by the growth temperature, composition, and substrate. The magnetic properties can be tailored by the substrate, as found by magnetic force microscopy imaging and vibrating sample magnetometry measurements. In addition to pronounced tetragonal deformations, depositing FeGa onto manganese nitride leads to the formation of stripe-like magnetic domain patterns and to the appearance of perpendicular magnetic anisotropy.

Antiferromagnetic MnN layer on the MnGa(001) surface

Spin polarized first principles total energy calculations have been applied to study the stability and magnetic properties of the MnGa(001) surface and the formation of a topmost MnN layer with the deposit of nitrogen. Before nitrogen adsorption, surface formation energies show a stable gallium terminated ferromagnetic surface. After incorporation of nitrogen atoms, the antiferromagnetic manganese terminated surface becomes stable due to the formation of a MnN layer (Mn-N bonding at the surface). Spin density distribution shows a ferromagnetic/antiferromagnetic arrangement in the first surface layers. This thermodynamically stable structure may be exploited to growth MnGa/MnN magnetic heterostructures as well as to look for exchange biased systems.

Ionothermal synthesis and magnetic study of a new manganese(ii) phosphite with an unprecedented Mn/P ratio

A new layered manganese(ii) phosphite, JIS-10, has been synthesised ionothermally; its structure features antiferromagnetic manganese dimers with S = 5/2.

Adverse effect of Mn doping on the magnetic ordering in Mn doped TiO2 nanoparticles

Herein, we have examined the role played by non-magnetic Mn on the magnetic properties of TiO2 nanoparticles. The samples display complete paramagnetic behavior at room temperature as well as at 10 K. Paramagnetism might be associated with the presence of isolated magnetic spins of Mn2+ in the system. Observation of negative Curie–Weiss temperature indicates presence of antiferromagnetic interaction in the system. Direct exchange interaction of Mn2+–Mn2+ and antiferromagnetic superexchange interaction of Mn2+ ions via lattice O2− ions contribute to antiferromagnetism. Surprisingly, ferromagnetism appears in pure and Mn doped (0.07 mol) TiO2 nanoparticles on vacuum calcination. Although Mn doped TiO2 displays ferromagnetism, there is a loss in magnetization as compared to the undoped TiO2. It is speculated that low growth temperature during vacuum calcinations might have resulted in amorphous MnO phase separation. This could result in competing ferromagnetic–antiferromagnetic interactions and overall reduction in magnetization. From the results it is evident that TiO2 could be made ferromagnetic by introducing sufficient concentration of oxygen vacancies in the system. Mn doping, however, has an adverse effect on the overall ferromagnetic ordering, as there is possibility of antiferromagnetic d–d exchange interaction of Mn2+ ions as well as possibility of antiferromagnetic manganese oxide phases separation.

Synthesis, structure, and characterizations of a new antiferromagnetic manganese(II) dichloro-bridged 1-D polymer decorated by 5-amino-1-H-tetrazole

[Mn(5-ATZ)2Cl2]n (1) (5-ATZ – 5-amino-1-H-tetrazole) was synthesized from the reaction of 5-ATZ and manganese(II) chloride and isolated by solution evaporation at room temperature. 1 was characterized by elemental analysis, X-ray crystallography, infrared, and EPR spectroscopy as well as magnetic measurements. In the crystal structure, [Mn(5-ATZ)2Cl2] units are linked by double μ2-bridging chlorides to form 1-D chains parallel to the a-axis. The Mn sphere approximates to octahedral with the metal coordinated by four chlorides in the equatorial plane and two 5-ATZ molecules, bound through their ring nitrogens, in axial positions. The intramolecular N–H···Cl hydrogen bond between the 5-ATZ amino group and the adjacent coordinated Cl− stabilizes the chain. N–H···N hydrogen bonds between adjacent chains form a 3-D supramolecular framework. No hyperfine coupling to the Mn nuclei (I = 5/2) is observed in the powdered EPR spectrum of 1 at 77 K. The frozen solution EPR spectrum provides evidence of the mononuclearity of 1 in methanol. The magnetic properties have been analyzed using the Hamiltonian H = –J∑Si · Si+1 with J = −1.38(3) cm−1 and g = 2.00(1). A small value of the exchange parameter is typical for 1-D six-coordinate bis(μ2-chloro) Mn(II) polymers.

Chemical synthesis and characterization of manganese oxide coated Ni particles

Nanosized Ni particles with an average diameter of about 8 nm were prepared by reducing of NiCl2 with sodium borohydride (NaBH4) in aqueous solution. By moderate annealing in protective atmosphere, the composite grew up to be 15–20 nm particles. Both of the as-prepared and annealed Ni particles were coated by a layer of manganese oxide via decomposition reaction in aqueous KMnO4 solution. Hysteresis loops of as-prepared samples show a large increase in the magnetization with decreasing temperature and an unsaturated component at high magnetic field. In contrast, the ferromagnetic characteristics of annealed one are much stronger with large magnetization and coercivity. The thermomagnetic curves verified the coexistence of ferromagnetic Ni and antiferromangetic Mn oxide phases. But there exists no exchange bias behavior in the samples, even though the interface structure between the ferromagnetic Ni core and the antiferromagnetic manganese oxides has been distinctly formed. The absence of exchange bias probably originates from the weak ferromagnetic characteristic of Ni cores.

Coupling the valley degree of freedom to antiferromagnetic order

Conventional electronics are based invariably on the intrinsic degrees of freedom of an electron, namely its charge and spin. The exploration of novel electronic degrees of freedom has important implications in both basic quantum physics and advanced information technology. Valley, as a new electronic degree of freedom, has received considerable attention in recent years. In this paper, we develop the theory of spin and valley physics of an antiferromagnetic honeycomb lattice. We show that by coupling the valley degree of freedom to antiferromagnetic order, there is an emergent electronic degree of freedom characterized by the product of spin and valley indices, which leads to spin-valley-dependent optical selection rule and Berry curvature-induced topological quantum transport. These properties will enable optical polarization in the spin-valley space, and electrical detection/manipulation through the induced spin, valley, and charge fluxes. The domain walls of an antiferromagnetic honeycomb lattice harbors valley-protected edge states that support spin-dependent transport. Finally, we use first-principles calculations to show that the proposed optoelectronic properties may be realized in antiferromagnetic manganese chalcogenophosphates (MnPX3, X = S, Se) in monolayer form.

Peculiarities of structural–phase states in ternary alloys Ni3(Mn, Ti)

The results of investigation of structural and physical properties of ternary alloys Ni3(Mn, Ti) are presented. A correlation between their physical and structural properties is revealed. The presence of a minimum is established in the curve for the long-range atomic order parameter in the superlattice L12 in the concentration dependence plot. It is assumed that an introduction of titanium would give rise to degradation of antiferromagnetic manganese–manganese interaction.

Influence of antiferromagnetic FeMn on magnetic properties of perpendicular magnetic thin films

We studied the influence of an anitferromagnetic FeMn layer on perpendicular magnetic anisotropy (PMA) and perpendicular coercivity ( H C⊥) of the CoCr/Pt multilayers and found that both PMA and H C⊥ can be enhanced by the FeMn layer. We observed an obvious exchange coupling between FeMn and CoCr/Pt multilayers which enhances PMA and may increase the density of pinning sites that can pin the domain wall of ferromagnetic layers and lifts up energy barrier during the propagation of domain walls. This leads to the enhancement of H C⊥. Moreover, X-ray diffraction results shows that the (111) texture of the FeMn layer enhances that of the CoCr/Pt multilayers, leading to the increase of PMA and H C⊥ as well. This result is of great significance on improving magnetic properties of perpendicular magnetic recording media by using an antiferromagnetic manganese alloy.

Antiferromagnetic iridium manganese based intermediate layers for perpendicular magnetic recording media

Current generation CoCrPt oxide based perpendicular magnetic recording media use two Ru-based intermediate layers in order to grow crystallographically textured, and magnetically isolated granular media. In this work, the advantage of replacing the Ru grain isolation layer with antiferromagnetic IrMn is demonstrated. Media samples using 7.5nm thick IrMn intermediate layers show perpendicular texture with dispersion below 4°, coercivity of over 4000Oe alongside magnetic exchange decoupling, average grain sizes of 6nm with distributions under 14%, and thermal stability factor of 88. The IrMn layer may also help to stabilize the recording layer grains against thermal instability effects.

Magnetic linear dichroism of an antiferromagnetic MnF2 crystal: Oddness in two different antiferromagnetic states

Dichroism of linearly polarized light propagating along the tetragonal C4 axis, induced by a longitudinal magnetic field, has been revealed in a tetragonal antiferromagnetic manganese fluoride crystal in the region of optical transitions. The magnetic linear dichroism observed is proportional to the magnetic field strength and odd with respect to the field sign. The value of the effect is sufficient for optical observation of antiferromagnetic domains in MnF2 crystals.

Crystal and magnetic structures of the antiferromagnetic manganese sulfide BaLa2MnS5 by powder neutron diffraction measurements

Powder neutron diffraction measurements were performed on an antiferromagnetic manganese sulfide BaLa2MnS5 at 7 and 100 K. This sulfide has a tetragonal nuclear structure with space group I/mcm. The neutron diffraction data at 7 K show a collinear antiferromagnetic structure (space group I) with a propagation vector k = (1/2, 1/2, 1/2). The magnetic moment of Mn2+ is estimated to be 4.21 μB and determined to lie in a parallel direction with the c-axis. The magnetic exchange constants, (2J1 + J2)/kB andJ3/kB, are estimated to be −6.6 K and 0.80 K, respectively, from the molecular field approximation.

Structure and Magnetic Behavior of a New Two-Dimensional Antiferromagnetic Manganese(II)-.mu.-1,3-Azido System

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructure and Magnetic Behavior of a New Two-Dimensional Antiferromagnetic Manganese(II)-.mu.-1,3-Azido SystemAlbert Escuer, Ramon Vicente, Mohamed A. S. Goher, and Franz A. MautnerCite this: Inorg. Chem. 1995, 34, 23, 5707–5708Publication Date (Print):November 1, 1995Publication History Published online1 May 2002Published inissue 1 November 1995https://doi.org/10.1021/ic00127a004RIGHTS & PERMISSIONSArticle Views192Altmetric-Citations92LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (260 KB) Get e-AlertsSupporting Info (2)»Supporting Information Supporting Information Get e-Alerts

Theory of the soliton-induced phase transition in quasi-one-dimensional magnets.

It is shown that the phase transition occurring in quasi-one-dimensional systems of weakly coupled magnetic chains with solitons in the form of \ensuremath{\pi} kinks is closely related to the properties of these solitons. The critical behavior of the systems considered corresponds to the critical behavior of the Ising model with the same dimension. The model describing the behavior of solitons below and above the critical temperature is presented. This model explains the experimental field dependence of the magnetization direction in the spin-flopping configuration for antiferromagnetic ${\mathrm{K}}_{2}$${\mathrm{FeF}}_{5}$. Application of the theory proposed here to the antiferromagnetic tetramethylammonium manganese trichloride (TMMC) allows one to explain the experimental field dependence of the N\'eel temperature.

Ferromagnetic resonance studies in the bilayer system Ni0.80Fe0.20/Mn0.50Fe0.50: Exchange anisotropy

Ferromagnetic resonance of Permalloy in the bilayer system Ni0.80Fe0.20/Mn0.50Fe0.50 has been used as a probe of the exchange anisotropy at the interface between the ferromagnetic Permalloy layer and the antiferromagnetic manganese iron. For rotation of the applied magnetic field in the plane of the film, the resonance condition exhibits a unidirectional anisotropy which relates directly to the exchange bias field, as measured, for example, by the shift of the hysteresis loop. In the perpendicular orientation, and for Permalloy layer thicknesses greater than about 400 Å, one or more standing spin wave modes are seen in addition to the uniform FMR. The indexing of these modes permit an evaluation of the boundary condition at the ferromagnet/antiferromagnet interface, in terms of partial spin pinning.

Energy Band Structure and Electronic Properties of NiAs Type Compounds. II. Antiferromagnetic Manganese Telluride

AbstractThe first calculation of the electron energy spectrum of antiferromagnetic MnTe is made using Green's function method. In accordance with the experiment MnTe is found to be a semiconductor with an indirect gap ≈0.8 eV and a direct gap of ≈1.26 eV. The results obtained confirm the validity of Allen's qualitative model for the MnTe energy structure. Special moments of symmetry are discussed. The semiconductor character is shown to be connected with antiferromagnetic order. The effective masses of valence band top electrons are calculated in the kp approximation and compared with the experiment.

Wavefunctions of two-particle collective excitations

A formalism is developed by which the wavefunctions, as well as the energies, of two-particle collective excitations may be obtained using the corresponding two-particle Green function. Using a simple one-dimensional model of a polyene chain, the wavefunction of an excitonic state is calculated. This calculation shows that the electron and hole are closely bound. A similar calculation is performed for the spin-wave mode in antiferromagnetic gamma manganese.

Dynamical susceptibilities in ferromagnetic and antiferromagnetic systems

Abstract The methods for calculating the collective excitations and dynamical susceptibilities in various models of itinerant-electron magnetism are reviewed. The local-exchange model and the model-Hamiltonian approach are discussed, and their advantages and disadvantages as applied to ferromagnetic and antiferromagnetic systems are brought out. Results are presented for a new many-band calculation of a generalised susceptibility corresponding to the case of fcc antiferromagnetic manganese.