Weak Ferromagnetism Research Articles

Substrate dependent epitaxy of superconducting niobium nitride thin films grown by pulsed laser deposition

Niobium nitride (NbN) has suitable mechanical properties for application as protective coatings in mechanical engineering, and also its superconductivity can be utilized in thin film devices for sensorics or in combination with ferromagnet in spintronics. Long-range superconducting proximity effect at the heterostructures with a weak ferromagnet can be used for generation of spin-polarized current. For any operational heterostructure application the high quality NbN thin films need to be prepared. In this work we have investigated impact of the substrates on the structure and preferential orientation of niobium nitride thin films fabricated by pulsed laser deposition at 600 °C on Si (001), MgO (001), C-plane and R-plane Al2O3 substrates. Growth parameters have been tuned in order to obtain single superconducting δ-NbN phase. Microstructure was analyzed by X-ray diffraction and transmission electron microscopy. Si substrate does not induce the film preferential orientation. Films on MgO are epitaxial (001) oriented. Films on R-Al2O3 show (135) orientation with twinned crystallites on the lower symmetry substrate surface. The (111) epitaxial growth with the largest crystallites and their smallest tilting was achieved on C-Al2O3 substrate leading to the best superconducting properties.

Peculiar magnetism of Bi1−xDyxFeO3 ceramics at the morphotropic phase boundary

• Bi 1−x Dy x FeO 3 samples were synthesized by solid-state reaction method. • Dy substitution causes the formation of the R3c / Pnma morphotropic phase boundary. • The pinched hysteresis loop and maximum magnetization are observed. • The metamagnetic transition of antiferromagnetic clusters explains for the pinched hysteresis loop. We report systematic studies on the crystal structure, optical phonons, and magnetic properties of Bi 1−x Dy x FeO 3 ( x = 0.1–0.2) systems at a morphotropic phase boundary (MPB) of R3c rhombohedral and Pnma orthorhombic structures. The structural phase coexistence is verified by observing two distinct X-ray diffraction profiles throughout the composition range. Rietveld refinement confirms the structural evolution from R3c to Pnma as the Dy concentration increases and provides details on the phase percentage and lattice parameters. Raman studies clearly reveal two different types of phonon vibrations in the coexisting phase. Weak ferromagnetism is observed in a composition with a dominant Pnma phase, meaning that the substitution of Dy weakly suppresses the cycloidal spin structure of the R3c phase. A pinched hysteresis loop is observed across the MPB and the magnetization reaches a maximum value and then decreases continuously as the Dy concentration increases. These observations are explained in the framework of the metamagnetic transition of antiferromagnetic clusters and the contribution of phase boundary spins.

Magnetic properties and spin reorientation of hexagonal HoFeO[formula omitted] thin films

We present structural, magnetic, and optical properties of hexagonal HoFeO3/Al2O3 thin films deposited by Magnetron Sputtering. The x-ray diffraction patterns of HoFeO3 thin films show the c-planes of a hexagonal structure. The magnetization data display an antiferromagnetic transition temperature, TN∼120 ± 5 K and the magnetization-field hysteresis loops were measured below 100 K, confirming a weak ferromagnetism arising from a spin canting of the Fe3+ moments. The magnetization data also show an anomaly around ∼40 K due to a spin-reorientation transition caused by the Ho3+- Fe3+ interactions. We observed comparable magnetization along the ab plane and c axis although the spin canting of Fe3+ sites has a preferential component along the c axis, suggesting that the Ho3+- Fe3+ interactions dominate in the low temperature magnetic structures of hexagonal-HoFeO3. The observed electronic excitations at ∼2.29, 2.87, 3.82, 4.79, and 6.53 eV have been assigned to the Fe3+d to d on-site as well as O 2p to Fe 3d, Ho 6s, and 5d charge-transfer excitations, respectively. The room temperature energy band gap of the hexagonal-HoFeO3 thin film was measured to be ∼1.99 ± 0.04 eV.

Distinct magnetic ground states of R2ZnIrO6 (R=La,Nd) determined by neutron powder diffraction

Double perovskite iridates $A_2$ZnIrO$_6$ ($A$ = alkaline or lanthanide) show complex magnetic behaviors ranging from weak ferromagnetism to successive antiferromagnetic transitions. Here we report the static ($dc$) and dynamic ($ac$) magnetic susceptibility, and neutron powder diffraction measurements for $A$ = La and Nd compounds to elucidate the magnetic ground state. Below 10~K, the $A$ = La compound is best described as canted iridium moments in an antiferromagnet arrangement with a propagation vector \textbf{k} = 0 and a net ferromagnetic component along the $c$-axis. On the other hand, Nd$_2$ZnIrO$_6$ is described well as an antiferromagnet with a propagation vector \textbf{k} = (1/2~1/2~0) below $T_\mathrm{N} \sim$ 17 K. Scattering from both the Nd and Ir magnetic sublattices were required to describe the data and both were found to lie almost completely within the $ab$-plane. $Dc$ susceptibility revealed a bifurcation between the zero-field-cooled and field-cooled curves below $\sim$13 K in Nd$_2$ZnIrO$_6$. A glassy state was ruled out by $ac$ susceptibility but detailed magnetic isotherms revealed the opening of the loop below 13~K. These results suggest a delicate balance exists between the Dzyaloshinskii-Moriya, crystal field schemes, and $d$-$f$ interaction in this series of compounds.

Tuning of magnetic properties and multiferroic nature: case study of cobalt-doped NdFeO3

Nanocrystalline NdFe1-xCoxO3 (0 ≤ x ≤ 0.4) samples have been synthesized by a sol–gel auto-combustion route. Rietveld refinement of x-ray diffraction patterns of the samples confirms the single-phase orthorhombic structure with space group Pbnm- $${D}_{2h}^{16}$$ . Williamson–Hall analysis is carried out to evaluate the average crystallite size and lattice strain. Raman scattering spectra indicate compressive strain with blueshift in doped samples. The particles that appeared in FESEM micrographs are found to be approximately spherical in shape, and the average size lies in the range of 32–58 nm. Pore radius and surface area of the powders have been determined by BET method. The room-temperature magnetic studies reveal a strong antiferromagnetic behavior with weak ferromagnetism due to Dzyaloshinskii–Moriya (D–M) exchange interaction mechanism. Cobalt doping enhances the magnitude of magnetization in NdFeO3 sample. The maximum magnetization (Mmax) is achieved to be 1.209 emu/g for 10% cobalt-doped sample. The deconvolution of M–H loop in ferromagnetic and antiferromagnetic parts has been performed. Room-temperature polarization–electric field (P–E) loops at different applied electric fields suggest the typical ferroelectric nature of all the samples. Maximum polarization (Pm) is found to be 1.09 μC/cm2 for x = 0.2 sample at 50 kV field. Temperature-dependent P–E loops exhibit an increase in coercive field (Ec) and polarization (P) with the increase in temperature, and this behavior indicates the growth in energy barrier for domain reorientation. Pore radius, density, and particle size have been correlated with magnetic and electrical properties of the nanocrystalline samples.

Room temperature ferromagnetism in multiferroic BaCoF[formula omitted] thin films due to surface, substrate and ion doping effects

Using a microscopic model and the Green’s function technique we have studied the influence of different surface, size and substrate effects on the magnetic properties of BaCoF4 thin films. The magnetization and the magnetic phase transition temperature increase for a compressible substrate Al2O3, whereas they decrease for a tensile substrate such as MgO. The film thickness influences also the magnetic properties. We have discussed a competition, a concurrence between the surface and substrate effects. Doping of bulk BaCoF4 with Al ions leads to weak room temperature ferromagnetism. Due to the magnetoelectric coupling is obtained that the polarization increases with increasing external magnetic field.

Structural and Magnetic Tuning of LaFeO3 Orthoferrite Substituted Different Rare Earth Elements to Optimize Their Technological Applications

Lanthanum partially substituted rare earth (RE) elements to form RE0.7La0.3FeO3; RE = Ce, Pr, Nd, Sm and Gd) nanoparticles. They were synthesized using the citrate–nitrate auto-combustion method. The crystal structure and microstructure were refined by applying Rietveld profile refinements using the Maud Program. The morphology, magnetic and optical properties of the inspected samples have been explored using HRTEM, VSM, and UV–Vis diffuse reflectance, respectively. The prepared-samples distortion increases as the substituted RE ionic radius decreases. Iron spins of RE orthoferrite samples are known to be ordered Anti-ferromagnetically (AFM). They also possess weak ferromagnetism due to the Dzyaloshinskii-Moriya interaction. This feeble ferromagnetism is reflected in their soft behavior, whereas Sm0.7La0.3FeO3 sample exhibits the butterfly shape hysteresis loop. The remnant magnetization, saturation magnetization, and coercivity are relatively small, but sometimes impressively, enhanced through Lanthanum-rare-earth substitution. Introducing rare earth ions into LaFeO3 decreases the Fe–O–Fe angle and the consequent reduction of the super exchange interaction. In particular, the coercivity of Sm0.7La0.3FeO3 is remarkably improved relative to the parent sample. It has the largest coercivity of all the prepared nanoparticles. Due to the aforementioned substitution, a slight reflectance edge red shift is observed in the spectra. The relation between the magnetic properties of the investigated samples and the ionic radii of RE was investigated and discussed. The experimental results of this work can provide fundamental support for the research and development of multiferroic materials.

Magnetic and electric properties of multiferroic LiFeP2O7. Comparison with LiCrP2O7

The temperature and magnetic field dependence of the magnetic and electric properties of LiFeP2O7 (LFPO) and LiCrP2O7 (LCPO) are studied using a microscopic model and the Green’s function technique. We have shown that LFPO is antiferromagnetic, but shows a weak ferromagnetism along the [Formula: see text] axis which originates from the canted antiferromagnetic order. For LCPO, such a ferromagnetic order along the [Formula: see text] axis is not observed. In the temperature dependence of the electrical polarization [Formula: see text] along the [Formula: see text] axis there is a kink at [Formula: see text] K which is an indirect evidence for the intrinsic magnetoelectric effect in LFPO. Applying an external magnetic field [Formula: see text], the polarization [Formula: see text] increases, stronger for small temperatures and the kink at [Formula: see text] disappears. For LCPO, we do not obtain a kink at [Formula: see text] K. LCPO is polar, but not ferroelectric. We can conclude that the missing magnetoelectric properties in LCPO could be due to the differences in the magnetic orders between LFPO and LCPO.

Size dependence of charge order and magnetism in Sm0.35Ca0.65MnO3

We report a systematic tracking of consequences of size decrease to nanoscale for charge order (CO) and magnetic properties of electron doped manganite Sm0.35Ca0.65MnO3 by magnetization measurements. The bulk form of this system is charge ordered below 270 K and antiferromagnetic (AFM) below 130 K. The bulk sample and nanoparticles of various sizes (mean diameter ∼ 15, 30, 90 nm) were synthesized by sol-gel technique. Our studies show that the robust CO in the bulk gets weakened by size reduction and the nanoparticles exhibit ferromagnetic (FM) ordering. Magnetization at high temperatures, in the paramagnetic region, reflecting the behaviour of the most part of the samples arising due to FM fluctuations caused by double exchange interaction is found to decrease as the particle size reduces. However, at low temperature the trend of FM magnetization as a function of the size is found to be reversed. This result is understood in terms of the dominance of surface effects where uncompensated bonds and an increase in the charge density at the surface layers lead to weak ferromagnetism which increases with decreasing size.

Effect of B-site Co substitution on the structure and magnetic properties of nanocrystalline neodymium orthoferrite synthesized by auto-combustion.

Samples of cobalt-doped neodymium orthoferrite compounds, NdCoxFe1−xO3 (0.0 ≤ x ≤ 0.5) were synthesized via glycine auto-combustion between 250 and 300°C and calcined at 500°C for 2 h. X-ray diffraction showed that all compounds had an orthorhombic perovskite structure with space group Pbnm. Increasing cobalt doping gradually reduced the lattice parameters and contracted the unit cell volume. Both X-ray diffraction and scanning electron microscopy showed that the particles were spherical and in the nano-sized range (19–52 nm) with pores between grains. Vibrating sample magnetometry at room temperature indicated that NdFeO3 has a high coercive field (1950 Oe) and cobalt substitution for iron led to a decrease in the coercive field, saturation and remanent magnetization, which was as a result of decreased magnetic moments in the crystal and reduced canting of the FeO6 octahedra. The increase in magnetization and coercive fields with increase of Co was connected to the microstructure (bond lengths and angles, defects, pores, grain boundaries) and crystallite size. The compounds NdCoxFe1−xO3 show antiferromagnetism with weak ferromagnetism due to uncompensated non-collinear moments. These compounds could serve as prototypes for tuning the properties of magnetic materials (ferromagnetic and antiferromagnetic) with potential applications in data storage, logic gates, switches and sensors.

Optical, photoluminescence and ferromagnetic properties of Ni-doped ZnO for optoelectronic applications

The current work presents the optical, photoluminescence and ferromagnetic properties of Zn1−xNixO samples with (0.00 ≤ x ≤ 0.20). The samples are well crystallizing in hexagonal wurtzite structure without a significant change in their lattice constants, while the crystallite size, grain size and number of unit cells in ZnO particle are increased. The residual stress is negative (compressive) and almost increases as Ni increases up to 0.10, but it is changed from negative to positive (tensile) at Ni = 0.20. The absorption and reflectance of UV spectra are increased as Ni increases up to 0.20. An absorption band centered at a wavelength of 552 nm is also observed and is gradually shifted by Ni towards longer wavelengths. Interestingly, two direct electronic transitions are found for all samples and two induced bandgaps which are decreased by Ni. While the other optical constants such as linear χ1 and non-linear third-order susceptibilities χ3, dispersion parameters (Ed, Eo), refractive indexes (no, n2), lattice dielectric constant eL, N/m*, optical and electrical conductivities (σopt, σele) are increased by Ni, the dissipation factor (tanδ) is decreased. Although some of the continuous peaks of lower PL intensities are recorded at UV band edges and slightly shifted to longer wave lengths (red shift) as Ni increases, strong UV emission peaks at about 390, 420 and 440 nm are recorded. Finally, the signature of a clear weak ferromagnetism ordering at room temperature, with evaluated magnetic parameters such as magnetization Ms, magnetic moments μ and magneto-crystalline anisotropy factor γ, is recorded for Ni ≥ 0.05 doped samples.

Effect of rare earth orthoferrite GdFeO3 on the band gap modulation and magnetic switching in Bi0.5Na0.5TiO3 ceramics

ABSTRACT This manuscript illustrates the structural, dielectric, optical and magnetic behaviour of [((Bi0.5Na0.5)1-xGdx)(Ti1-xFex)O3] O3 [BNTGF], x = 0.0,0.1, 0.2, 0.3, 0.4 and 0.5 prepared by mixed-oxide technique. The structural and phase identification is confirmed by X-ray diffraction, Scanning electron microscopy, Fourier transform infrared Spectroscopy and Raman analysis. The dielectric constants of the GdFeO3 modified ceramics are less than the reported values of the parent materials. Inverse variation of ferroelectric properties such as remnant polarization (Pr ) and coercive field (Ec) with GdFeO3 doping is clear from room temperature hysteresis loops. Appearance of weak ferromagnetism in the samples is established from the room temperature magnetic hysteresis loops due to the carrier-mediated exchange interactions with smaller values of magnetic parameters. The energy gap of the materials obtained from UV-vis spectra shows a drastic decrease compared to that of pure Bi0.5Na0.5TiO3.

Enhanced high temperature ferromagnetism in Bi1−x R x FeO3 (R = Dy, Y) compounds

In this work we report experimental evidence for the weak high-temperature ferromagnetism in Bi1−x R x FeO3 (R = Dy, Y) compounds by systematic characterizations, excluding the possible side-effects from other iron-based impurities. Remarkable saturated magnetic moment was observed in the Y-substituted samples, Bi1−x Y x FeO3, which is larger than the moment obtained in Bi1−x Dy x FeO3, the Dy-substituted samples with antiferromagnetic background. The physical origin of the weak ferromagnetic transition is discussed and serious lattice distortions have been identified based on the x-ray diffraction and Raman scattering data, although the rhombohedral structure symmetry remains unchanged upon the substitutions. It is believed that the structural distortion suppressed cycloid spin structure is the main factor for the enhanced magnetization in Bi1−x R x FeO3 compounds. Additionally, the Dy3+–Fe3+ antiferromagnetic coupling, which strengthens the antiferromagnetic interaction in Bi1−x Dy x FeO3 compounds, acts as the driving force for the magnetic discrepancy between Bi1−x Y x FeO3 and Bi1−x Dy x FeO3 samples.

Proximity Effect in Heterostructures Based on a Superconductor/Half-Metal System

We demonstrated that with increasing the exchange splitting of the conduction band of a ferromagnet and, respectively, of the degree of the spin polarization, the probability of transmission of the superconducting Cooper pairs through the S/F interface decreases. We concluded that the spin imbalance plays a key role in the processes taking place at the interface between a superconductor and a ferromagnet with spin-polarized conduction electrons. We have studied the superconducting spin-valve effect in F1/F2/S heterostructures containing the Heusler alloy Co2Cr1−xFexAly as one of two ferromagnetic (F1 or F2) layers. We used the Heusler alloy layer in two roles: as a weak ferromagnet on the place of the F2 layer and as a half-metal on the place of the F1 layer. In the first case, we obtained the full switching between the normal and superconducting states is realized with the dominant aid of the long-range triplet component of the superconducting pair condensate which occurs at the perpendicular mutual orientation of magnetizations. In the second case, we observed separation between the superconducting transitions for perpendicular and parallel configurations of magnetizations reaching 0.5 K. We also find a good agreement between our experimental data and theoretical results.

Symmetry Origin of the Dzyaloshinskii-Moriya Interaction and Magnetization Reversal in YVO3.

We have investigated magneto-structural phase transitions in polycrystalline YVO3 using high-resolution neutron powder diffraction toward understanding the phenomenon of magnetization reversal. Contrary to earlier reports, our study reveals that both C-type and G-type antiferromagnetic ordering, corresponding to G-type and C-type orbital ordered phases, respectively, occur at the same temperature (TN = 115 K) with the G-type antiferromagnetic phase growing at the expense of the C-type one on cooling. These processes cease at TS ∼ 77 K; however, a minor (∼4%) untransformed C-type phase remains unchanged down to 1.7 K. The symmetry analysis indicates different symmetry origins of the Dzyaloshinskii-Moriya interaction in each phase, which can explain the magnetization reversal observed between TN and TS. We discuss that magnetic phase separation and associated weak ferromagnetism may be the common mechanism underlying the magnetization reversal phenomenon observed in other RVO3 systems (R = rare earth).

Structural evolution and magnetic properties in Bi1-xNdxFeO3 ceramics

Ceramic Bi1-xNdxFeO3 solid solutions in the composition range of 0.10 ≤ x ≤ 0.20 were prepared to study the structural evolution and magnetic properties. The structural analysis of X-ray diffraction (XRD) and Rietveld refinement data revealed only a phase transition from the polar R3c rhombohedral to antipolar Pbam orthorhombic structures, while Raman scattering (RS) spectroscopy not only detected the phonon vibrations of the R3c and Pbam symmetries in the samples 0.10 ≤ x ≤ 0.16 but also found the phonon vibrations of the orthorhombic Pbam and Pbnm symmetries for x ≥ 0.16. The magnetic properties of these compounds revealed the weak ferromagnetism at high doping concentration. This observation indicated a crucial role of the destruction of the cycloidal spin structure for revealing the weak ferromagnetism. The magnetic aging behavior observed at room temperature confirmed the contribution of phase boundary spins to the magnetic properties.

Influence of Ni doping on physical properties of La0.7Sr0.3FeO3 synthesized by reverse micelle technique

In the present work, a series of Ni-doped La0.7Sr0.3FeO3 perovskite nanostructures with chemical composition La0.7Sr0.3Fe1−xNixO3 (x = 0.0, 0.01 and 0.04) were synthesized by the reverse micelle (RM) technique. The X-ray diffraction (XRD) analysis verifies good crystallinity and an orthorhombic crystal structure of the samples. The remarkable growth of the crystallites was observed in increasing the amount of Ni doping. The morphology, topography, and chemical composition were investigated through field emission scanning electron microscope (FESEM) equipped with an energy dispersive X-ray spectrometer (EDS). The FESEM/EDS measurements confirm uniform morphology and interconnected nature of the particles with relevant elements. The Fourier transform infrared (FTIR) spectra further demonstrate the perovskite structure through Fe/Ni–O asymmetric stretching and deformation of Fe/Ni–O–Fe/Ni bending vibrations in the lattice. A systematic reduction in the bandgap (Eg) is noticed upon the Ni doping in La0.7Sr0.3FeO3, as estimated from the UV/visible spectra by employing the Tauc's relation. A distinct behaviour of dielectric properties was revealed as a function of frequency and temperature for all the samples. The dielectric constant (e′), dielectric loss (tanδ), and ac conductivity (σac) were measured at selected frequencies and temperatures. The results signify that the dielectric nature was frequency-dependent and thermally stimulated. The magnetic properties at room temperature indicate weak ferromagnetism with gradual increase in the maximum magnetization and coercivity with the increase in Ni concentration.

Synthesis of hexagonal-shaped Cr3C2@C nanoplatelets and role of their intrinsic properties towards microwave absorption

Core-shell nanomaterials have been considered excellent microwave absorbents due to their unique morphologies and designs. Here, hexagonal-shaped Cr3C2 nanoplatelets coated with carbon shells (Cr3C2@C) were fabricated by an arc discharge plasma process. In as-synthesized Cr3C2@C nanoplatelets a weak ferromagnetism is found with an observable coercivity of 38 Oe, a saturation magnetization of 4 × 10−1 emu/g, and along with a suitable conductivity of 9.56 × 102 Ω−1cm−1. The observed suitable electrical conductivity and inductive magnetism of Cr3C2@C nanoplatelets played a vital role as a magnetic and conductive losses. Intrinsic defect-rich Cr3C2 cores and amorphous carbon shells acted as dielectric polarization centers, wherein the incident electromagnetic wave dissipated through polarization and interfacial losses. The Cr3C2@C nanoplatelets with 30 wt% loadings in the paraffin matrix exhibited a minimum reflection loss of −36.9 dB at the thickness of 1.6 mm. The excellent refelection loss performance of Cr3C2@C nanoplatelets was certified to be a result from the synergetic effects of dielectric/magnetic losses and impedance matching. Furthermore, the Cr3C2@C nanoplatelets exhibited oxidation resistivity at 350 °C endorsing their application in harsh atmospheres.

Evidence of Weak Ferromagnetism, Space Charge Polarization, and Metal to Insulator Transition in Dy-Doped CaMnO3

The effect of Dy doping on CaMnO3 (CDMO) has been thoroughly investigated. The room-temperature structure, low-temperature magnetic transitions, and high-temperature electrical properties of CDMO were studied using X-ray diffraction, magnetization, and dielectric techniques. The CDMO exhibits an orthorhombic structure with Pnma symmetry. The low-temperature magnetic susceptibility data show the ferromagnetic domains embedded in the antiferromagnetic structure (G-type), and it confirms the Neel temperature (TN) approximately 55 K. Temperature-dependent dielectric data measured using a few selected frequencies show a high dielectric constant ~ 29,108,808 at 1 kHz. The presence of a high dielectric constant at the lower frequency side can be attributed to the space charge polarization (SCP) and compositional disorder (heterogeneity) in the compounds. The impedance cole-cole plot shows a depressed semicircle; mathematically these data were fitted by the Kohlrausch-Williams-Watt model. From this model obtained two mechanisms: (i) the electric modulus divulges the CDMO ceramic tails the Non-Debye type of relaxation and (ii) the electric modulus peak shifting evidence the charge carrier mobility from long range to short range. High-temperature dielectric, resistivity, and conductivity data show a clear anomaly around 461 K, owing to metal to insulator transition.

Ferro- vs. antiferromagnetic exchange between two Ni(II) ions in a series of Schiff base heterometallic complexes: what makes the difference?

Three new NiII/ZnII heterometallics, [NiZnL'2(OMe)Cl]2 (1), [NiZnL''(Dea)Cl]2·2DMF (2) and [Ni2(H3L''')2(o-Van)(MeOH)2]Cl·[ZnCl2(H4L''')(MeOH)]·2MeOH (3), containing three-dentate Schiff bases as well as methanol or diethanolamine (H2Dea) or o-vanillin (o-VanH), all deprotonated, as bridging ligands were synthesized and structurally characterized. The Schiff base ligands were produced in situ from o-VanH and CH3NH2 (HL'), or NH2OH (HL"), or 2-amino-2-hydroxymethyl-propane-1,3-diol (H4L'''); a zerovalent metal (Ni and Zn in 1, Zn only in 2 and 3) was employed as a source of metal ions. The first two complexes are dimers with a Ni2Zn2O6 central core, while the third compound is a novel heterometallic cocrystal salt solvate built of a neutral zwitterionic ZnII Schiff base complex and of ionic salt containing dinuclear NiII complex cations. The crystal structures contain either centrosymmetric (1 and 2) or non-symmetric di-nickel fragment (3) with NiNi distances in the range 3.146-3.33 Å. The exchange coupling is antiferromagnetic for 1, J = 7.7 cm-1, and ferromagnetic for 2, J = -6.5 cm-1 (using the exchange Hamiltonian in a form Ĥ = Jŝ1ŝ2). The exchange interactions in 1 and 2 are comparable to the zero-field splitting (ZFS). High-field EPR revealed moderate magnetic anisotropy of opposite signs: D = 2.27 cm-1, E = 0.243 cm-1 (1) and D = -4.491 cm-1, E = -0.684 cm-1 (2). Compound 3 stands alone with very weak ferromagnetism (J = -0.6 cm-1) and much stronger magnetic anisotropy with D = -11.398 cm-1 and E = -1.151 cm-1. Attempts to calculate theoretically the exchange coupling (using the DFT "broken symmetry" method) and ZFS parameters (with the ab initio CASSCF method) were successful in predicting the trends of J and D among the three complexes, while the quantitative results were less good for 1 and 3.