Intralayer Ferromagnetic Interactions Research Articles

Spin-wave analysis of the ferromagnetic-ferromagnetic Heisenberg spin bilayer with intralayer single-ion anisotropy and interlayer antiferromagnetic interaction

In this paper, the spin wave theory is applied to the Heisenberg spin bilayer with intralayer ferromagnetic interaction [Formula: see text], intralayer single-ion anisotropy D and interlayer antiferromagnetic interaction [Formula: see text]. It is found that the effects of both D and [Formula: see text] on the thermodynamic quantities give rise to the two different low-temperature asymptotic behaviors with and without exponential law. For [Formula: see text], the interlayer antiferromagnetic interaction can induce the appearance of the maximum of the layer magnetization at finite temperatures. At the location of the layer magnetization maximum, the approximate behaviors (such as the power, linear, rational, exponential and logarithmic laws) which are driven by the temperature or the anisotropy, are obtained for the low-temperature thermodynamic properties. It is shown that the presence of antiferromagnetic interlayer interaction [Formula: see text] clearly induces more quantum fluctuations than the case where the interlayer interaction [Formula: see text] is ferromagnetic. Our results of the layer magnetization agree with the experimental data of the layered van der Waals crystal FeCl2 at low temperatures. In the monolayer case of [Formula: see text], our results are in agreement with the findings obtained by the existing theories and the quantum Monte Carlo data.

A NiII–WV(CN)8 layer magnet showing metamagnetic behavior

Abstract By crystal engineering of molecular magnets, unique magnetic functionalities can be intentionally designed. In this work, we synthesized a novel two-dimensional cyanido-bridged coordination network, [NiII(pz)4]{[NiII(pz)3][WV(CN)8]}2·3.5H2O (NiW, pz = pyrazole), which exhibits metamagnetic behavior. NiW has wavy coordination layers created by two differently sized molecular square ladders and exhibits strong intralayer ferromagnetic interactions. Nevertheless, due to the relatively short interlayer distance, NiW shows spontaneous antiferromagnetic ordering below a Néel temperature of 21 K. By applying an external magnetic field, such antiferromagnet can be converted into a ferromagnet with a coercive field of 600 Oe at 2 K, elucidating the metamagnetic behavior of NiW.

Theoretical Analysis of Magnetic Coupling in the Ti2C Bare MXene.

The nature of the electronic ground state of the Ti2C MXene is unambiguously determined by making use of density functional theory-based calculations including hybrid functionals together with a stringent computational setup providing numerically converged results up to 1 meV. All the explored density functionals (i.e., PBE, PBE0, and HSE06) consistently predict that the Ti2C MXene has a magnetic ground state corresponding to antiferromagnetic (AFM)-coupled ferromagnetic (FM) layers. A spin model, with one unpaired electron per Ti center, consistent with the nature of the chemical bond emerging from the calculations, is presented in which the relevant magnetic coupling constants are extracted from total energy differences of the involved magnetic solutions using an appropriate mapping approach. The use of different density functionals enables us to define a realistic range for the magnitude of each of the magnetic coupling constants. The intralayer FM interaction is the dominant term, but the other two AFM interlayer couplings are noticeable and cannot be neglected. Thus, the spin model cannot be reduced to include nearest-neighbor interactions only. The Néel temperature is roughly estimated to be in the 220 ± 30 K, suggesting that this material can be used in practical applications in spintronics and related fields.

Quantum Spin-1/2 Dimers in a Low-Dimensional Tetrabromocuprate Magnet.

This work describes a homometallic spin‐1/2 tetrabromocuprate adopting a bilayer structure. Magnetic‐susceptibility measurements show a broad maximum centred near 70 K, with fits to this data using a Heisenberg model consistent with strong antiferromagnetic coupling between neighbouring copper atoms in different layers of the bilayer. There are further weak intralayer ferromagnetic interactions between copper cations in neighbouring dimers. First‐principles calculations are consistent with this, but suggest there is only significant magnetic coupling within one direction of a layer; this would suggest the presence of a spin ladder within the bilayer with antiferromagnetic rung and weaker ferromagnetic rail couplings.

A Three-Dimensional Coordination Framework with a Ferromagnetic Coupled Ni(II)-CrO4 Layer: Synthesis, Structure, and Magnetic Studies.

We report herein on the crystal structure and magnetic studies of a three-dimensional (3D) Ni(II)-chromate coordination polymer, [Ni(CrO4)(bpym)(H2O)]n (1; bpym = 5,5′-bipyrimidin), prepared by self-assembly of Ni(II) and chromate ions with a multi-N donor auxiliary ligands, bpym, through hydrothermal processes. The structure of 1 is composed of Ni(II)-CrO4 layers with [Ni3(μ3-CrO4)] triangular motifs, in which the Ni(II) centers are bridged by O′:O′:O′:μ3-CrO42− anions, and the resulting layers are further connected by twisted trans-μ2-N,N′-bpym auxiliary ligands to form a 3D pillar-layered network with an hms topology. The magnetic properties of compound 1 were illustrated by variable field and temperature magnetic susceptibility measurements. The findings reveal that compound 1 shows intralayer ferromagnetic interactions within Ni(II)-CrO4 layers, and furthers the 3D antiferromagnetic ordering in the resulting of interlayer antiferromagnetic couplings with a Néel temperature (TN) of 5.6 K. In addition, compound 1 shows the field-induced metamagnetic behavior at temperature below the TN.

Malonate-Containing Manganese(III) Complexes: Synthesis, Crystal Structure, and Magnetic Properties of AsPh4[Mn(mal)2(H2O)2

The novel manganese(III) complexes PPh4[Mn(mal)2(H2O)2] (1) and AsPh4[Mn(mal)2(H2O)2] (2) (PPh4+ = tetraphenylphosphonium cation, AsPh4+ = tetraphenylarsonium cation, and H2mal = malonic acid) have been prepared, and the structure of 2 was determined by X-ray diffraction analysis. 2 is a mononuclear complex whose structure is made up of trans-diaquabis(malonato)manganate(III) units and tetraphenylarsonium cations. Two crystallographically independent manganese(III) ions (Mn(1) and Mn(2)) occur in 2 that exhibit elongated octahedral surroundings with four oxygen atoms from two bidentate malonate groups in equatorial positions (Mn(1)-O = 1.923(6) and 1.9328(6) A and Mn(2)-O = 1.894(6) and 1.925(6) A) and two trans-coordinated water molecules in the axial sites (Mn(1)-Ow = 2.245(6) A and Mn(2)-Ow = 2.268(6) A). The [Mn(mal)2(H2O)2]- units are linked through hydrogen bonds involving the free malonate-oxygen atoms and the coordinated water molecules to yield a quasi-square-type anionic layer growing in the ab plane. The shortest intralayer metal-metal separations are 7.1557(7) and 7.1526(7) A (through the edges of the square). The anionic sheets are separated from each other by layers of AsPh4+ where sextuple- and double-phenyl embraces occur. The magnetic behavior of 1 and 2 in the temperature range 1.9-290 K reveals the occurrence of weak intralayer ferromagnetic interactions (J = +0.081(1) (1) and +0.072(2) cm(-1) (2)). These values are compared to those of the weak antiferromagnetic coupling [J = -0.19(1) cm(-1)], which is observed in the chain compound K2[Mn(mal)2(MeOH)2][Mn(mal)2] (3), where the exchange pathway involves the carboxyate-malonate bridge in the anti-syn conformation. The structure of 3 was reported elsewhere. Theoretical calculations on fragment models of 2 and 3 were performed to analyze and substantiate both the nature and magnitude of the magnetic couplings observed.

Study on photomagnetism of 2-D magnetic compounds coupled with photochromic diarylethene cations

Intercalation of an organic photochromic molecule into the magnetic system provides multifunctionalities such as photomagnetism. In order to build up a photosensitive multifunctional-material, we have synthesized an organic-inorganic hybrid system consisting of layered-perovskite-type copper halides and photochromic diarylethenes. By mixing the stoichiometric amounts of CuCl 2 and 2,2′-dimethyl-3,3′-(perfluorocyclopentene-1,2′-diyl)bis-(benzo-[b]thiophene-6-ammonium)( 1) in aqueous hydrochloric acid and methanol solution, we obtained ( 1)CuCl 4. In the dark synthetic condition, the resulting compound with open-form 1a has an intralayer ferromagnetic interaction whose exchange coupling constant is estimated at J/ k B = 10.7 K. Additionally, this compound shows antiferromagnetic transition at T N = 3 K because of the antiferromagnetic interaction between adjacent sheets. In UV irradiated synthetic condition, the resulting compound with close-form 1b has a weaker intralayer ferromagnetic interaction ( J/ k B = 6.9 K) and shows no magnetic phase transition above 2 K. By the photo-irradiation, we can control the antiferromagnetic transition and the intralayer magnetic interaction.

Fine structure of the light absorption spectrum of antiferromagnetic NaMnCl3

A fine structure of the optical absorption spectrum of antiferromagnetic NaMnCl3 was measured around 23800 cm−1 at temperatures in the range 1.8–50 K in magnetic fields up to 200 kOe. The fact that the intralayer ferromagnetic interaction in the crystal possessing a layered magnetic structure is stronger than the interlayer antiferromagnetic interaction leads to the formation of intensive hot exciton-magnon absorption bands. The special features of the exciton-magnon band structure in the crystal are connected with the special features of magnon dispersion and density of exciton-magnon states.

Powder neutron diffraction analysis and magnetic structure of kagomé-type vanadium jarositeNaV3(OD)6(SO4)2

Neutron and x-ray diffraction experiments were performed on pure, deuterated samples of the vanadium jarosite compound, ${\mathrm{NaV}}_{3}(\mathrm{OD}{)}_{6}({\mathrm{SO}}_{4}{)}_{2},$ to investigate its structure and magnetism. The crystal structure was refined using combined single-crystal x-ray and powder neutron diffraction methods. To determine the magnetic structure, neutron powder diffraction measurements were performed at 217 and 16 K. Analysis of the data reveals that the unpaired spins located on the ${\mathrm{V}}^{3+}$ ions couple ferromagnetically within the ${\mathrm{V}}_{3}(\mathrm{OD}{)}_{6}({\mathrm{SO}}_{4}{)}_{2}^{\ensuremath{-}}$ triangles of the Kagom\'e layers with the spins oriented parallel to the layers. Spins in adjacent layers order antiferromagnetically. The temperature dependence of magnetic diffraction peak intensities yields a zero-field critical transition temperature of ${T}_{c}=34.3(5)\mathrm{K}.$ The intralayer ferromagnetic interaction propagates along the Kagom\'e lattice via the \ensuremath{\pi}-symmetry orbitals of a -$[{\mathrm{V}}^{3+}\ensuremath{-}\mathrm{OD}\ensuremath{-}{\mathrm{V}}^{3+}]$- pathway.

{[Cu(H2O)3][Cu(phmal)2]}n: a new two-dimensional copper(ii) complex with intralayer ferromagnetic interactions (phmal = phenylmalonate dianion)

The novel sheet-like copper(II) compound of formula {[Cu(H2O)3][Cu(Phmal)2]}n (1) (Phmal = dianion of phenylmalonic acid) has been synthesized and its crystal structure determined by X-ray diffraction. The structure of 1 consists of 21 chains of carboxylate(phenylmalonate)-bridged copper(II) ions which are linked through double μ-oxo(carboxylate) units to afford a two-dimensional network. The interlayer space is filled by the phenyl rings of the phenylmalonate ligands that exhibit offset face-to-face interactions. Variable-temperature magnetic measurements of 1 show the occurrence of significant intralayer ferromagnetic interactions between the copper(II) ions through anti–syn carboxylate- and double μ-oxo-bridges which are analyzed and discussed in the light of the values found in related magneto-structurally characterized systems.

ChemInform Abstract: NaV3(OH)6(SO4)2: A Kagome‐Type Vanadium(III) Compound with Strong Intralayer Ferromagnetic Interactions.

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Intercalation of stable organic radicals into layered copper hydroxides

We report the intercalation of a stable organic radical, 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidine-1-oxyl anion (PROXYL −) into the layered copper hydroxides, Cu 2(OH) 3(CH 3CO 2)·H 2O, by means of the anion exchange. The powder X-ray diffractions reveal the anion exchange, showing an increase in the interlayer distance. However, the elemental analyses indicate that the obtained material is Cu 2(OH) 3.5(PROXYL) 0.5·H 2O. The temperature dependence of the magnetic susceptibilities for the intercalation compound indicates a dominant antiferromagnetic interaction in contrast to the intralayer ferromagnetic interaction in the parent compound. The EPR spectra of the intercalation compound consist of the absorption of the organic radical, whose temperature-variable follows the Curie law. The observed antiferromagnetic properties can be ascribed to a transition in the magnetic properties of the [Cu 2(OH) 3] + layer from ferromagnetic to antiferromagnetic upon intercalation.

NaV3 (OH)6 (SO4 )2 : A Kagomé-Type Vanadium(III) Compound with Strong Intralayer Ferromagnetic Interactions.

A dominant ferromagnetic exchange interaction propagates about the magnetic sites of the Kagomé lattice of the title compound through the bridging hydroxy groups (see section of the structure). This is at variance with the antiferromagnetic exchange observed for jarosite and its derivatives. The ferromagnetism probably arises from the d2 electron count of the VIII centers.

NaV3(OH)6(SO4)2: A Kagomé-Type Vanadium(III) Compound with Strong Intralayer Ferromagnetic Interactions

NaV3(OH)6(SO4)2: A Kagomé-Type Vanadium(III) Compound with Strong Intralayer Ferromagnetic Interactions

Controllable magnetic properties of layered copper hydroxides, Cu 2(OH) 3X (X=carboxylates)

Physical and chemical properties of organic/inorganic hybrid nanocomposites are attractive, because they are potential materials yielding new functionality, such as a cooperative phenomenon, multi-functional property and so on. Layered copper hydroxides, Cu 2(OH) 3X (X=carboxylate anions), are two dimensional magnetic materials whose structures consist of alternating stacking of the magnetic copper hydroxides layer and the carboxylate layer. In this paper we report the preparations, structures and magnetic properties of various copper hydroxides. In the series of Cu 2(OH) 3( n-C m H 2 m+1 COO), the carboxylate anions form an interdigitated monolayer in the m=0 and 1 materials, while those do a bilayer in the m=6–11 materials. The intermediate materials ( m=2–5) exhibit both mono- and bi-layer structures, which are governed by the condition at their preparations. The temperature dependence of the paramagnetic susceptibilities of the m=0 and 1 materials suggests an intralayer ferromagnetic interaction, while that of the m=6–11 materials does an antiferromagnetic interaction. Further, the longer alkyl chain materials show a divergence of the ac magnetic susceptibility at 22 K, indicating a ferromagnetic order. It is found that the materials show a drastic change in magnetism, depending on the molecular orientation of the carboxylate anions. The Cu K-edge EXAFS spectroscopy at 20 K indicates a characteristic difference in local structure between the shorter and the longer alkyl chain materials, they are large enough to explain the drastic magnetic change. In this report, we also show controllable magnetic properties of Cu 2(OH) 3(8-(( p-(phenylazo)phenyl)oxy)octanoate), derived from cooperation between the inorganic layer carrying magnetism and the organic layer playing a role of sensor. A reversible structural transformation occurs as a result of soaking in hot methanol and acetonitrile. The X-ray diffraction patterns indicate that the organic layer in the material exhibits an interdigitated monolayer structure in hot methanol, while it does a membrane-like bilayer structure in acetonitrile. The monolayer phase is paramagnetic down to 3 K, while the bilayer phase shows a ferromagnetic order below 10.8 K. The reversible packing change of the organic guest molecules results in the drastic modification in the magnetic properties of the inorganic layer. The material in the bilayer phase exhibits a trans-to- cis isomerization reaction of the azobenzene moiety by UV light illumination, although there is little change of the magnetic properties after the photoreaction. The photoreaction is irreversible under irradiation of VIS light.

Magnetic Properties of Cu2(OH)3(alkanecarboxylate) Compounds: Drastic Modification with Extension of the Alkyl Chain

Magnetic properties of the layered materials Cu2(OH)3(n-CmH2m+1COO) (m = 0, 1, 7, 8, and 9) have been examined. X-ray powder diffraction patterns indicate that the interlayer distance increases in the order of m. The interlayer distances of the m = 0 and 1 materials are shorter than the molecular heights of the intercalated carboxylates, respectively, while the distances of the m = 7−9 materials are nearly double those of the molecular heights of the corresponding carboxylates, indicating a bilayer structure in them. The temperature dependence of the paramagnetic susceptibilities of the m = 0 and 1 materials suggests an intralayer ferromagnetic interaction and an interlayer antiferromagnetic interaction. The metamagnetic behavior is supported by S-shape dependence of their magnetization curves. The temperature dependence of the paramagnetic susceptibilities of the m = 7−9 materials indicates an intralayer antiferromagnetic interaction, in opposition to those in the former two. Further, they show a diverge...