Interchain Antiferromagnetic Interactions Research Articles

Spin-Flop Transition in a Nickel–Octacyanidotungstate Chain Magnet

Crystal engineering of molecular magnetic materials often leads to novel magnetic functionalities. In this study, we synthesized an ionic chain magnet, i.e., [NiII(imi)6]{[NiII(imi)4][WV(CN)8]}2·4H2O (imi = imidazole; NiW) comprising anionic cyanido-bridged [NiII(imi)4WV(CN)8]nn– chains and cationic mononuclear [NiII(imi)6]2+ complexes. Ferromagnetic coupling between NiII and WV with S = 1 and 1/2, respectively, via a bridging cyanido ligand is found within the chain. However, the total magnetization of NiW is canceled out by a notable antiferromagnetic interchain interaction below a Néel temperature of 8.5 K. Such an antiferromagnetic interaction can be overcome by applying an external magnetic field of 0.9 T at 2 K, and a steep spin-flop transition is observed. From a crystal engineering perspective, we attribute this metamagnetic behavior to the isolated [NiII(imi)6]2+ complex that attracts the chains to be close to each other. Additionally, the complex operates as an independent paramagnetic spin source that offers an extra magnetization state of this compound.

Transition metal halide complexes of 4′-aminoacetophenone: Syntheses, structures, and magnetic behavior

A family of eight compounds of the general formula [(C8H9NO)2MX2] or [(C8H9NO)2(H2O)2MX2], (M = Ni, Co, Cu, Zn; X = Cl, Br) has been prepared and the compounds characterized by combustion analysis, IR, single-crystal X-ray diffraction and variable temperature magnetization measurements. [[(C8H9NO)2(H2O)nMX2], (1, n = 0, M = Cu, X = Cl; 2, n = 0, M = Cu, X = Br; 3, n = 2, M = Ni, X = Cl; 4, n = 2, M = Ni, X = Br; 5, n = 2, M = Co, X = Cl; 6, n = 2, M = Co, X = Br; 7, n = 0, M = Zn, X = Cl; 8, n = 0, M = Zn, X = Br.) The eight compounds crystallize in three distinct space groups and have coordination number of either four (compounds 1, 2, 7, and 8) or six (compounds 3–6). Compounds 1 and 2 are slightly distorted square planar, compounds 3–6 are slightly distorted octahedral, and compounds 7 and 8 are slightly distorted tetrahedral. All eight compounds form chains either through bihalide interactions (1 and 2) or systems of hydrogen bonds (3–8). Chains are linked into layers through short halide…halide (1, 2, 7) and both traditional and non-traditional hydrogen bonds. The complexes have also been studied via variable temperature magnetic susceptibility measurements. Data for Cu(II) complexes 1 and 2 the 1D-Heisenberg uniform chain model with J/kB of −13.4(6) K and −14.3(4) K, respectively, with antiferromagnetic interchain interactions (θ = −4.1(5) K, −2.5(5) K, respectively) following the H=-J∑si∙sj Hamiltonian. The Ni(II) and Co(II) compounds showed temperature dependent moments which were well-modeled as arising due to single-ion anisotropy.

Experimental and theoretical investigation of structure-magnetic properties relationships in a new heteroleptic one-dimensional triple bridged azido/acetato/DMSO copper (II) coordination polymer

We report the synthesis, structure, and magnetic investigation of a novel one-dimensional copper (II) coordination polymer: formula [Cu(μ1,1N3)(μ1,3OAc)(μ-DMSO)]∞ (1) (OAc=acetate). The connection between neighbouring copper ions arises through a triple bridge involving EO type azide, syn–syn carboxylate and μ-DMSO molecule in apical positions forming an elongated octahedral coordination of copper ions. Magnetic susceptibility measurements show that complex (1) exhibits ferromagnetic intrachain interactions Jchain = +66 cm−1 whereas a metamagnetic behaviour occurs below 2.1 K related with antiferromagnetic inter-chain interactions with a critical field of 600 Oe at 1.8 K. DFT calculations were caried out to rationale the in-chain ferromagnetic interactions between copper ions. We found that the ferromagnetic coupling between copper ions is less sensitive to variation of bond length and/or Cu-N-Cu angle that may be caused by external stimulus such as temperature or pressure.

Ligand Modified and Light Switched On/Off Single-Chain Magnets of {Fe 2 Co} Coordination Polymers via Metal-to-Metal Charge Transfer

Ligand Modified and Light Switched On/Off Single-Chain Magnets of {Fe ₂ Co} Coordination Polymers via Metal-to-Metal Charge Transfer

Magnetic field and pressure phase diagrams of the triangular-lattice antiferromagnet CsCuCl3 explored via magnetic susceptibility measurements with a proximity-detector oscillator

The effect of pressure ($P$) on magnetic susceptibility of ${\mathrm{CsCuCl}}_{3}$ was examined in magnetic fields (${\ensuremath{\mu}}_{0}H$) of up to 51 T using a proximity-detector oscillator (PDO), and the $H\text{\ensuremath{-}}P$ phase diagram of ${\mathrm{CsCuCl}}_{3}$ was constructed over the saturation field (${H}_{\mathrm{sat}}$). We found that, with increasing $P, {H}_{\mathrm{sat}}$ increases and the up-up-down phase that appeared at $P=0.7\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ widened. Based on comparison between the experimental and calculated $H\text{\ensuremath{-}}P$ phase diagrams, the Y phase was predicted to appear above 1.7 GPa. The interchain antiferromagnetic exchange interaction in the $ab$ plane was evaluated and found to increase with increasing $P$, which is consistent with a previous study under high pressure [D. Yamamoto et al., Nat. Commun. 12, 4263 (2021)]. Moreover, an anomaly was observed below $P=0.6\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ just below ${H}_{\mathrm{sat}}$ and might be a new phase transition derived from nonlinear response caused by the PDO technique.

An Uneven Chain-like Ferromagnetic Copper(II) Coordination Polymer Displaying Metamagnetic Behavior and Long-Range Magnetic Ordering

Ferromagnetic coupling exists in an uneven chain-like copper(II) complex with both end-on azido and syn-syn carboxylato bridges, (Cu3(L)2(N3)4(H2O)3)n (1, HL = 6-hydroxynicotinic acid). It is the first example of one-dimensional (1D) chain-like copper(II) coordination polymer showing both metamagnetic behavior and long-range magnetic ordering (Tc = 6.7 K), thanks to the interchain hydrogen bonds, which make a three-dimensional (3D) supramolecular array of the entire molecular structure and mediate the interchain antiferromagnetic interaction.

Thermal and magnetic properties and optical spectroscopy of SmCr3(BO3)4

We measured the heat capacity, magnetic susceptibility, magnetization, magnetoelectric effect, and optical spectra of samarium chromium borate crystals. It was found that, in $\mathrm{Sm}{\mathrm{Cr}}_{3}{(\mathrm{B}{\mathrm{O}}_{3})}_{4}$ single crystals, structures with the space groups $R32$ and $C2/c$ may coexist. Magnetic phase transitions were discovered at temperatures ${T}_{\mathrm{N}1}=7.8\ifmmode\pm\else\textpm\fi{}0.5\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, ${T}_{\mathrm{N}2}=6.7\ifmmode\pm\else\textpm\fi{}0.5\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, and ${T}_{3}=4.3\ifmmode\pm\else\textpm\fi{}0.2\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, and assumptions about their nature were made. Based on the high-resolution optical spectra and magnetometry data, the crystal-field parameters in the ${\mathrm{Sm}}^{3+}$ and ${\mathrm{Cr}}^{3+}$ positions and the parameters of ${\mathrm{Cr}}^{3+}\text{\ensuremath{-}}{\mathrm{Cr}}^{3+}$ and ${\mathrm{Cr}}^{3+}\text{\ensuremath{-}}{\mathrm{Sm}}^{3+}$ exchange interactions were determined. The magnetic properties of the quasi-one-dimensional chromium subsystem were analyzed in the frame of the previously developed self-consistent four-particle cluster model. Despite a strong suppression of ${\mathrm{Cr}}^{3+}$ magnetic moments by the interchain antiferromagnetic exchange interactions, the contributions of the chromium subsystem to the bulk magnetization are dominant.

Multifunctional Ni(II)-Based Metamagnetic Coordination Polymers for Electronic Device Fabrication.

The combination of two 8-aminoquinoline-based Schiff base ligands (L1 and L2) with SCN- and Ni(II) has led to the synthesis of two new one-dimensional thiocyanato-bridged coordination polymers: [Ni(L1)(NCS)2]n (1) and [Ni(L2)(NCS)2]n (2). Both compounds are isostructural and consists of regular zigzag thiocyanato-bridged chains with very weak S···S interchain interactions. The measured room-temperature conductivities of compounds 1 and 2 (7.0 × 10-5 and 2.0 × 10-5 S m-1, respectively) are indicative of semiconductor behavior which increases in the presence of photoillumination (3.5 × 10-4 and 4.9 × 10-4 S m-1, respectively). The measured I-V characteristics of compound 1 and 2 based thin film metal-semiconductor (MS) junction devices under irradiation and nonirradiation conditions show a nonlinear rectifying behavior, typical of a Schottky diode (SD). The rectification ratios (Ion/Ioff) of the SDs in the dark at ±2 V (26.96 and 31.96 for 1- and 2-based devices, respectively) increase to 44.19 and 79.42, respectively, upon light irradiation. The photoinduced behavior has been analyzed by thermionic emission theory, and to determine the diode parameters, the Cheung's method has been employed. These diode parameters indicate that compound 2 has a better performance in comparison to compound 1 and that these materials are good candidates for applications in electrochemical devices. Magnetic measurements show that both compounds present ferromagnetic Ni-Ni intrachain and weak antiferromagnetic interchain interactions. The isothermal magnetizations at 2 K show that both compounds are metamagnets with critical fields of ca. 130 mT in 1 and 90 mT in 2 at 2 K. In the ferromagnetic phase (above the critical field), both compounds exhibit a long-range ferromagnetic order with critical temperatures of around 3.5 K in 1 and 3.0 K in 2. DC and AC measurements with different applied DC fields confirm the metamagnetic behaviors and have allowed the determination of the magnetic phase diagram in both compounds.

A Delicate Balance between Antiferromagnetism and Ferromagnetism: Theoretical and Experimental Studies of A2 MRu5 B2 (A=Zr, Hf; M=Fe, Mn) Metal Borides.

Metal-rich borides with the Ti3 Co5 B2 -type structure represent an ideal playground for tuning magnetic interactions through chemical substitutions. In this work, density functional theory (DFT) and experimental studies of Ru-rich quaternary borides with the general composition A2 MRu5 B2 (A=Zr, Hf, M=Fe, Mn) are presented. Total energy calculations show that the phases Zr2 FeRu5 B2 and Hf2 FeRu5 B2 prefer ground states with strong antiferromagnetic (AFM) interactions between ferromagnetic (FM) M-chains. Manganese substitution for iron lowers these antiferromagnetic interchain interactions dramatically and creates a strong competition between FM and AFM states with a slight preference for AFM in Zr2 MnRu5 B2 and for FM in Hf2 MnRu5 B2 . Magnetic property measurements show a field dependence of the AFM transition (TN ): TN is found at 0.1 T for all phases with predicted AFM states whereas for the predicted FM phase it is found at a much lower magnetic field (0.005 T). Furthermore, TN is lowest for a Hf-based phase (20 K) and highest for a Zr-based one (28 K), in accordance with DFT predictions of weaker AFM interactions in the Hf-based phases. Interestingly, the AFM transitions vanish in all compounds at higher fields (>1 T) in favor of FM transitions, indicating metamagnetic behaviors for these Ru-rich phases.

Controlling Ferromagnetic Ground States and Solitons in Thin Films and Nanowires Built from Iron Phthalocyanine Chains

AbstractIron phthalocyanine (FePc) is a molecular semiconductor whose building blocks are 1D ferromagnetic chains. It is shown that its optical and magnetic properties are controlled by the growth strategy, obtaining extremely high coercivities of over 1 T and modulating the exchange constant between 15 and 29 K through switching from thin films with controlled orientations, to ultralong nanowires. Magnetization measurements are analyzed using concepts and formulas with broad applicability to all 1D ferromagnetic chains. They show that FePc is best described by a xy model with moments preferentially lying in the molecular planes. The chain Hamiltonian is very similar to that for the classic inorganic magnet CsNiF3, but with ferromagnetic rather than antiferromagnetic interchain interactions. The dominant degrees of freedom are topological excitations called solitons, namely moving 1D magnetic domain walls, and at low temperatures and fields a “super‐Curie–Weiss” law characteristic of nearly 1D xy and Heisenberg ferromagnets, where susceptibility scales as 1/(T2–θ2), is observed. The ability to control the molecular orientation and ferromagnetism of FePc systems, and produce them on flexible substrates, together with excellent transistor characteristics reported previously for phthalocyanine analogues, makes them potentially useful for magneto‐optical and spintronic devices.

Excitations in the spin-1 trimer chain compound CaNi3P4O14 : From gapped dispersive spin waves to gapless magnetic excitations

Magnetic excitations and the spin Hamiltonian of the spin-1 J1-J1-J2 trimer chain compound CaNi3P4O14 have been investigated by inelastic neutron scattering. Experimental data reveal gapped dispersive spin wave excitations in the 3D long-range ordered magnetic state (TC = 16 K), and gapless magnetic excitations above the TC. Simulated magnetic excitations, by using the linear spin wave theory, for a model of coupled trimer spin-chains provide a good description of the observed experimental data. The analysis reveals both ferromagnetic J1 and J2 interactions within the chains, and an antiferromagnetic interchain interaction J3 between chains. The strengths of the J1 and J2 are found to be closer (J2/J1 ~ 0.81), and J3 is determined to be weaker (J3/ J1 ~ 0.69), which is consistent with the spin chain type crystal structure. Presence of a weak single-ion-anisotropy (D/J=0.19) is also revealed. The strengths and signs of exchange interactions explain why the 1/3 magnetization is absent in the studied spin-1 compound CaNi3P4O14 in contrast to its S= 5/2 counterpart Mn based isostructural compound. The signs of the exchange interactions are in agreement with that obtained from the reported DFT calculations, whereas, their strengths are found to be significantly different. The relatively strong value of the J3 in CaNi3P4O14 gives a conventional 3D type magnetic ordering below the TC, however, retains its 1D character above the TC. The present experimental study also reveals a sharp change of single-ion anisotropy across the TC indicating that the stability of the 3D magnetic ordering in CaNi3P4O14 is ascribed to the local magnetic anisotropy in addition to interchain interactions. The present study divulges the importance of full knowledge of the exchange interactions in trimer spin chain compounds to understand their exotic magnetic properties, such as 1/3 magnetization plateau.

Magnetic properties of a GdCr3(BO3)4 single crystal

The temperature dependence of the magnetic susceptibility χ (T) of the GdCr3(BO3)4 single crystal was studied in the temperature range of 2–300 K for two orientations of the external magnetic field: H ǁ c and H ± c. It was established that gadolinium chromium borate is ordered antiferromagnetically at TN = 7 K. It was found that, at T > 10 K, the magnetic properties of the crystal are isotropic, which is characteristic of the pure spin states of Cr3+ and Gd3+ ions. It was demonstrated that the magnetic susceptibility χ(T) of the GdCr3(BO3)4 compound at T > TN is well described by a one-dimensional spin model for a system of ferromagnetic chains of Cr3+ ions with ferromagnetic exchange 2J/k = −13.6 K and antiferromagnetic interchain interaction of 2J′/k = + 0.72 K. The gadolinium subsystem is antiferromagnetically biased due to the exchange f-d-interaction, which gives θGd=−2.8K. It was assumed that the GdCr3(BO3)4 compound is an antiferromagnet with “easy-plane” type anisotropy in the magnetically ordered state.

Structures, Thermodynamic Relations, and Magnetism of Stable and Metastable Ni(NCS)2 Coordination Polymers.

Reaction of Ni(NCS)2 with 4-aminopyridine in different solvents leads to the formation of compounds with the compositions Ni(NCS)2(4-aminopyridine)4 (1), Ni(NCS)2(4-aminopyridine)2(H2O)2 (2), [Ni(NCS)2(4-aminopyridine)3(MeCN)]·MeCN (3), and [Ni(NCS)2(4-aminopyridine)2] n (5-LT). Compounds 1, 2, and 3 form discrete complexes, with octahedral metal coordination. In 5-LT the Ni cations are linked by single thiocyanate anions into chains, which are further connected into layers by half of the 4-aminopyridine coligands. Upon heating, 1 transforms into an isomer of 5-LT with a 1D structure (5-HT), that on further heating forms a more condensed chain compound [Ni(NCS)2(4-aminopyridine)] n (6) that shows a very unusual chain topology. If 3 is heated, a further compound with the composition Ni(NCS)2(4-aminopyridine)3 (4) is formed, which presumably is a dimer and which on further heating transforms into 6 via 5-HT as intermediate. Further investigations reveal that 5-LT and 5-HT are related by enantiotropism, with 5-LT being the thermodynamic stable form at room-temperature. Magnetic and specific heat measurements reveal ferromagnetic exchange through thiocyanate bridges and magnetic ordering due to antiferromagnetic interchain interactions at 5.30(5) K and 8.2(2) K for 5-LT and 6, respectively. Consecutive metamagnetic transitions in the spin ladder compound 6 are due to dipolar interchain interactions. A convenient formula for susceptibility of the ferromagnetic Heisenberg chain of isotropic spins S = 1 is proposed, based on numerical DMRG calculations, and used to determine exchange constants.

Spin-wave dynamics and exchange interactions in multiferroic NdFe3(BO3)4 explored by inelastic neutron scattering

Magnetic excitations and exchange interactions in multiferroic NdFe3(BO3)4 were studied by inelastic neutron scattering in the phase with commensurate antiferromagnetic structure. The observed spectra were analyzed in the frame of the linear spin-wave theory. It was shown that only the model, which includes the exchange interactions within eight coordination spheres, describes satisfactorily all observed dispersion curves. The calculation showed that the spin-wave dynamics is governed by the strongest antiferromagnetic intra-chain interaction and three almost the same inter-chain interactions. Other interactions, including ferromagnetic exchange, appeared to be insignificant. The overall energy balance of the antiferromagnetic inter-chain exchange interactions, which couple the moments from the adjacent ferromagnetic layers as well as within a layer, stabilizes ferromagnetic arrangement in the latter. It demonstrates that the pathway geometry plays a crucial role in forming of the magnetic structure.

A Series of Chiral, Polar, Homospin Topological Ferrimagnets: M3(OOCH)5Cl(OH2) (M = Fe, Co, Ni)

An isostructural series of transition metal-formate-chloride-hydrate compounds, M3(OOCH)5Cl(OH2) (M = Fe, Co, Ni), have been synthesized using a solvothermal method. These compounds crystallize in the chiral and polar space group P31 and are comprised of three different types of helical chains of edge-sharing M2+-centered octahedra. All three compounds undergo 3D ferrimagnetic ordering at low temperature, and the iron and cobalt analogues exhibit field-induced metamagnetic transitions. The magnetic structure was determined by neutron powder diffraction, revealing ferromagnetic intrachain coupling and antiferromagnetic interchain interactions, with the three chains arranged in a two-up/one-down triangular lattice. As all three chains contain one type of metal in the same spin state, these compounds are rare examples of homospin topological ferrimagnets.

Slow Magnetic Relaxation in One-Dimensional Azido-Bridged CoII Complexes.

Crystal structures and magnetic properties of three one-dimensional (1D) azido-bridged cobalt(II) chains with different amide ligands (L), [Co2(N3)4(DMF)3] (1), [Co4(N3)8(DEF)5] (2), and [Co2(N3)4(DIPF)2] (3) (DMF = N,N-dimethylformamide, DEF = N,N-diethylformamide, and DIPF = N,N-diisopropylformamide), are reported to investigate the influence of L on their structures and magnetic properties. Single-crystal X-ray crystallographic analysis revealed that, although 1-3 all consist of cobalt chains bridged by end-on (EO) azides, the coordination geometry of the CoII ions and the repeating units of the 1D structures are quite different. As the size of L increases, the ratio of L to CoII decreases from 6:4 in 1 to 5:4 and 4:4 in 2 and 3, respectively. In 1, two [CoN5O1] and two [CoN4O2] distorted octahedra form the {[CoN5O1][CoN4O2]2[CoN5O1]} tetramers (denoted as Co4A), which are linked to each other by sharing the N-N edge to form the chain. Similarly, the chain structure of 3 is constructed from a similar tetramer unit {[CoN5][CoN4O2]2[CoN5]} (denoted as Co4B), where half of the CoII centers are in the [CoN5] trigonal bipyramid because of the larger steric effect of the DIPF ligand, while, for compound 2 of the medium-sized amide, it has the transition structure between those of 1 and 3. The chain is composed of two different repeating units: Co4A unit similar to that in 1 and Co4B unit similar to that in 3. Because of their similar structures, compounds 1-3 exhibit analogical magnetic properties. Direct-current magnetic measurements demonstrated that all compounds show intrachain ferromagnetic coupling through the EO azides and interchain anti-ferromagnetic interactions. Alternating-current data revealed the slow magnetic relaxation in the anti-ferromagnetic ordered phases. While compound 1 exhibits spin glass behavior, compounds 2 and 3 behave as the single-chain magnets. This difference might come from the interference of the anti-ferromagnetic ordering on the magnetic dynamic of the magnetic chain.

Magnetic phase diagram of the organic antiferromagnet F4BImNN

We present a combination of heat capacity and ac susceptibility measurements as a function of temperature and field, of a single crystal of the radical 2-(4,5,6,7-tetrafluorobenzimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl. Our results confirm a zero-field Néel temperature at TN(0)=0.73K and allow the determination of the critical field parameters Hc(||)=170Oe and Hc(⊥)=306Oe. Assuming the previously determined 1-D intrachain ferromagnetic exchange interaction of Jintra/k=+22K between radicals, the interchain antiferromagnetic interaction is calculated as zJinter/k∼−0.03K.

Magnetic behavior of cobalt bromide hydrates including a deuterated form

The magnetic properties of little examined CoBr2•2H2O and new CoBr2•H2O and CoBr2•D2O are studied. Curie-Weiss fits, χM=C/(T-θ), yield θ of −9.9, 9.4 and 10.0 K, respectively, over a 30–80 K linear range for each. Higher temperature data are fit assuming two moderately separated low lying Kramers doublets, with exchange accounted for in a mean-field approximation. Susceptibility maxima appear at 9.5, 15.4 and 15.5 K, with χmax of 0.163, 0.375 and 0.435emu/mol, respectively. Antiferromagnetic ordering is estimated to occur at 9.0, 13.7 and 13.8 K, in the same order. The ratio Tc/Tmax is 0.95, 0.89 and 0.89, respectively, suggesting little low dimensional magnetic character in singly hydrated systems. Data at lower temperatures for the dihydrate are fit with an antiferromagnetic 3D-Ising model. For singly hydrated systems the large size of χmax prevents this; weakened interchain antiferromagnetic interactions yield enhanced susceptibility maxima. Magnetization data exhibit field induced transitions near 13.5kG for the dihydrate, and near 6.5kG for singly hydrated systems with enhanced hysteresis. These transitions are interpreted as metamagnetic in nature.

Halide Influence on Molecular and Supramolecular Arrangements of Iron Complexes with a 3,5-Bis(2-Pyridyl)-1,2,4,6-Thiatriazine Ligand

A series of iron centered complexes, namely, [Fe(Py2TTA)Cl2] (1), [Fe(Py2TTA)Br2] (2), and [Fe(μ-F)(Py2TTAO)F]∞ (3), were isolated via complexation of 3,5-bis(2-pyridyl)-1,2,4,6-thiatriazine (Py2TTAH) with various ferric halides (e.g., FeF3, FeCl3, and FeBr3). Comparison of the optical and electrochemical spectroscopy, structural analysis, and magnetic studies reveal numerous similarities between the chlorido (1) and bromido (2) derivatives, which crystallize as discrete five-coordinate iron centered complexes with coordination geometries that are intermediate between trigonal bipyramidal and square base pyramid. Conversely, the fluorido derivative (3) results in a completely different structure due to oxidation of the ligand and the formation of a one-dimensional coordination polymer held together through a bridging fluoride ion. Consequently, the spectroscopic and magnetic behavior of 3 differs significantly compared with 1 and 2. Complexes 1 and 2 exhibit paramagnetic properties typical for a mononuclear S = 5/2 system with weak intermolecular antiferromagnetic interactions at low temperatures, whereas complex 3 demonstrates significant exchange couplings within the chain and weak antiferromagnetic interchain interactions, which stabilize a canted antiferromagnetic state below 4.2 K.

Synthesis, crystal growth, structural and magnetic characterization of NH4MCl2(HCOO), M=(Fe, Co, Ni)

An ambient-pressure solution route and an improved solvothermal synthetic method have been developed to produce polycrystalline powders and large single crystals of NH4MCl2(HCOO) (M=Fe, Co, Ni). The magnetic structure of the 1D linear chain compound NH4FeCl2(HCOO) has been determined by low-temperature neutron powder diffraction, revealing ferromagnetic intra-chain interactions and antiferromagnetic inter-chain interactions. The newly-reported Co and Ni analogs are isostructural with NH4FeCl2(HCOO), but there are significant differences in the magnetic properties of each compound; the Ni analog behaves similarly to the Fe compound but with stronger magnetic coupling, exhibiting antiferromagnetic ordering (TN=8.5K) and a broad metamagnetic transition between 2 and 5T, while the Co analog does not order magnetically above 2K, despite strong antiferromagnetic nearest-neighbor interactions.