Dc Susceptibility Measurements Research Articles

Probing the Magnetization Relaxation Dynamics of Four-Coordinate Lanthanide(III) Complexes

The reaction of bulky trimethylsilylanilide (N-TMSA) ligand with various lanthanide salts led us to isolate unusual and unique four-coordinate monomeric Ln(III) complexes which are challenging to isolate and not surprisingly rare in the literature. The single crystal X-ray diffraction unveils that all the complexes are monomeric and isostructural with the general molecular formula of [Ln(N-TMSA)3(THF)] where Ln = Dy (1) or Yb (2). Both complexes are found to possess distorted tetrahedral geometry. For all the complexes, detailed dc and ac susceptibility measurements were performed and both 1 and 2 show frequency-dependent out-of-phase susceptibility signals only in the presence of an optimum external magnetic field. The experimental observations are well supported by theoretical calculations and developed magneto-structural correlation using the various model complexes.

Evidence for cluster glass ground state in the potential giant dielectric constant material Ba(Fe1/2Sn1/2)O3-δ

We report the magnetic ground state of the technologically important giant dielectric constant material Ba(Fe1/2Sn1/2)O3-δ (BFSO) using detailed dc and ac magnetization and specific heat measurements. Our careful x-ray diffraction analysis confirms that BFSO is single phase and crystallizes in the cubic structure with the Pm3¯m space group. Temperature-dependent dc susceptibility measurements reveal that magnetic irreversibility sets in below Tirr ~ 18 K. In addition, the zero-field cooled susceptibility exhibits a peak at the freezing temperature Tf ~ 16 K, which is also characterized by a frequency dispersion in ac susceptibility measurements. This data also confirms to the critical slowing down model with cluster-glass transition temperature TG ~15.7 K and characteristic relaxation time τo ~10−7 s. The magnetic field dependence of the freezing temperature Tf obeys de Almeida-Thouless line in the H-T plane. The presence of aging effect and extremely slow time decay of thermoremanent magnetization is also observed below Tf. The magnetic contribution to the specific heat (Cm) exhibits a linear temperature dependence below Tf. All these observations unambiguously confirm a cluster-glass magnetic ground state in this system.

High-Pressure Synthesis of High-Entropy Metal Disulfides with Pyrite-Type Structure

We succeed in synthesizing equimolar-multi metal solid solutions of (Fe, Co, Ni, Cu)S2 and (Fe, Co, Ni, Cu, Ru)S2 by sintering at 900 °C under 2–4 GPa. These were stabilized by the high-entropy effect. Nevertheless, (Fe, Co, Ni, Cu, M)S2 (M = Zn, Mn, or Cd) was not obtained as single phase under the same synthetic conditions, mostly owing to the relatively large ionic radius of M2+. Single-crystal X-ray diffraction analysis shows that (Fe, Co, Ni, Cu)S2 crystallizes into a pyrite type with the space group \(Pa\bar{3}\) (#205) [a = 5.777(3) Å], randomly distributed at one site. The results of electrical resistivity and magnetic dc-susceptibility measurements indicate that both (Fe, Co, Ni, Cu)S2 and (Fe, Co, Ni, Cu, Ru)S2 are metals with ferrimagnetic ordering below Tc = 130 K. The band structure and the projected density of states (Fe, Co, Ni, Cu)S2, were obtained by density functional theory calculations in a high-entropy representative supercell, supporting the experimental results.

Spin-glass behavior in Li3NiCuBiO6: a two-dimensional distorted honeycomb-lattice

We report a detailed experimental study on the structural and magnetic properties of Li3NiCuBiO6 by means of various characterization techniques. It crystallizes into a monoclinic crystal structure composed of a layered magnetic honeycomb lattice along the c-axis. The existence of glassy state below 4 K is indicated by dc and ac susceptibility measurements. Magnetic contribution to the total heat capacity also peaks around the freezing temperature, and its linear temperature dependence backs our claim of a glassy state in the compound. The calculated magnetic entropy unveils that only ∼26% of the total entropy is released for the system (), and a tremendous amount of spin entropy is still retained in the system. Further, analysis of the frequency-dependent freezing temperature with the help of power law confirms the presence of a spin glass state. Moreover, the appearance of magnetic memory and relaxation effect below freezing temperature manifest the development of the system via a large number of intermediate metastable states. All these measurements confirm the spin-glass behavior of the compound. We consider the presence of different magnetic atoms in honeycomb lattice as the main driving factor for the spin-glass ground state.

Anomalous Ferromagnetic Behavior in Orthorhombic Li3Co2SbO6.

Monoclinic Li3Co2SbO6 has been proposed as a Kitaev spin liquid candidate and investigated intensively, whereas the properties of its polymorph, the orthorhombic phase, are less known. Here we report the magnetic properties of orthorhombic Li3Co2SbO6 as revealed by dc and ac magnetic susceptibility, muon spin relaxation (μSR), and neutron diffraction measurements. Successive magnetic transitions at 115, 89, and 71 K were observed in the low-field dc susceptibility measurements. The transitions below TN (115 K) are suppressed at higher applied fields. However, zero-field ac susceptibility measurements reveal distinct frequency-independent transitions at about 114, 107, 97, 79, and 71 K. A long-range magnetic ordered state was confirmed by specific heat, μSR, and neutron diffraction measurements, all indicating a single transition at about 115 K. The discrepancy between different measurements is attributed to possible stacking faults and/or local disorders of the ferromagnetic zigzag chains, resulting in ferromagnetic boundaries within the overall antiferromagnetic matrix.

A Tetranuclear Dysprosium Schiff Base Complex Showing Slow Relaxation of Magnetization

A tetranuclear dysprosium Schiff base complex was isolated by reacting dysprosium chloride with 2-hydroxy-3-methoxybenzaldehyde and 2-(aminomethyl)pyridine in-situ under basic conditions. The isolated Dy(III) complex was characterized by elemental analyses, single crystal X-ray diffraction and molecular spectroscopy. The complex crystallizes in the triclinic space group P-1 with unit cell parameters of a = 10.2003 (4), b = 13.8602 (5), c = 14.9542 (6), α = 94.523 (3), β = 109.362 (4), and γ = 99.861 (3). The magnetic properties of 1 have been investigated by DC and AC susceptibility measurements. The DC measurements reveal weak exchange coupling of antiferromagnetic nature. In the AC measurement, the complex shows a slow relaxation of magnetization in the absence of an external magnetic field.

Antiferromagnetic short-range order and cluster spin-glass state in diluted spinel ZnTiCoO4

The nature of magnetism in the doubly-diluted spinel ZnTiCoO4 = (Zn2+) A [Ti4+Co2+] B O4 is reported here employing the temperature and magnetic field (H) dependence of dc susceptibility (χ), ac susceptibilities (χ′ and χ″), and heat capacity (C p) measurements. Whereas antiferromagnetic (AFM) Néel temperature T N = 13.9 K is determined from the peak in the ∂(χT)/∂T vs T plot, the fit of the relaxation time τ (determined from the peak in the χ″ vs T data at different frequencies) to the Power law: τ = τ 0 [(T − T SG)/T SG]−zν yields the spin glass freezing temperature T SG = 12.9 K, z ν ∼ 11.75, and τ 0 ∼ 10−12 s. Since the magnitudes of τ 0 and z ν depend on the magnitude of T SG, a procedure is developed to find the optimum value of T SG = 12.9 K. A similar procedure is used to determine the optimum T 0 = 10.9 K in the Vogel–Fulcher law: τ = τ 0 exp[E a/k B(T − T 0)] yielding E a/k B = 95 K, and τ 0 = 1.6 × 10−13 s. It is argued that the comparatively large magnitude of the Mydosh parameter Ω = 0.026 and k B T 0/E a = 0.115 (≪1) suggests cluster spin-glass state in ZnTiCoO4 below TSG. In the C p vs T data from 1.9 K to 50 K, only a broad peak near 20 K is observed. This and absence of λ-type anomaly near T N or T SG combined with the reduced value of change in magnetic entropy from 50 K to 1.9 K suggests only short-range AFM ordering in the system, consistent with spin-glass state. The field dependence of T SG shows slight departure (ϕ ∼ 4.0) from the non-mean-field Almeida–Thouless line T SG(H) = T SG(0) (1 − AH 2/ϕ ). Strong temperature dependence of magnetic viscosity S and coercivity H C without exchange bias, both tending to zero on approach to T SG from below, further support the spin-glass state which results from magnetic dilution driven by diamagnetic Zn2+ and Ti4+ ions leading to magnetic frustration. Magnetic phase diagram in the H–T plane is established using the high-field magnetization data M(H, T) for T < T N which reveals rapid decrease of T SG with increase in H whereas decrease in T N with increase in H is weaker, typical of AFM systems. For T > T N, the data of χ vs T are fit to the modified Curie–Weiss law, χ = χ 0 + C/(T + θ), with χ 0 = 3.2 × 10−4 emu mol−1 Oe−1 yielding θ = 4 K and C = 2.70 emu K mol−1 Oe−1. This magnitude of C yields effective magnetic moment = 4.65 μ B for Co2+, characteristic of Co2+ ions with some contribution from spin–orbit coupling. Molecular field theory with effective spin S = 3/2 of Co2+ is used to determine the nearest-neighbor exchange constant J 1/k B = 2.39 K AFM and next-nearest-neighbor exchange constant J 2/k B = −0.66 K (ferromagnetic).

On the magnetic structure and magnetic behaviour of the most distorted member of the series of RNiO3 perovskites (R = Lu).

The crystal structure of LuNiO3 perovskite has been examined below RT and across TN = 125 K by neutron powder diffraction. In this temperature region (2-298 K), well below the metal-insulator transition this oxide exhibits at TMI = 599 K, this material is insulating and characterized by a partial charge disproportionation of the Ni valence. In the perovskite structure, defined in the monoclinic P21/n space group, there are two inequivalent Ni sites located in alternating octahedra of different sizes. The structural analysis with high-resolution techniques (λ = 1.594 Å) unveils a subtle increase of the charge disproportionation as temperature decreases, reaching δeff = 0.34 at 2 K. The magnetic structure has been investigated from low-T NPD patterns collected with a larger wavelength (λ = 2.52 Å). Magnetic peaks are observed below TN; they can be indexed with a propagation vector k = (½, 0, ½), as previously observed in other RNiO3 perovskites for the Ni sublattice. Among the three possible solutions for the magnetic structure, the first one is discarded since it would correspond to a full charge ordering (Ni2+ + Ni4+), with magnetic moments only on Ni2+ ions, not compatible with the structural findings assessing a partial charge disproportionation. The best agreement is found for a non-collinear model with two different moments in Ni1 and Ni2 sites, 1.4(1) μB, and m 0.7(1) μB at 2 K, the ordered magnetic moments lying on the a-c plane. This is similar to that found for YNiO3. In complement, the magnetic and thermal properties of LuNiO3 have been investigated. AC susceptibility curves exhibit a clear peak centered at TN = 125 K, corresponding to the establishment of the Ni antiferromagnetic structure. This is corroborated by DC susceptibility and specific heat measurements. Magnetization vs. field measurements confirm that the system is antiferromagnetic down to 2 K, without any further magnetic change. This linear behavior is also observed in the paramagnetic regime (T > TN).

Magnetic properties and evidence of a new spin-glass transition induced by Mn-doping in Tb2NiSi3

It is extremely rare for the coexistence of two spin glass transitions in single phase materials. In the present paper, the structure and magnetic properties of Tb2Ni0.8Mn0.2Si3 were investigated. For comparison, the corresponding experimental results of Tb2NiSi3 compound were also provided. In the temperature dependence of dc susceptibility measurements, there are two anomaly transitions for both Tb2Ni0.8Mn0.2Si3 and Tb2NiSi3. Further studies on the frequency dependence of ac susceptibility show a new spin-glass transition at 14 K in Tb2Ni0.8Mn0.2Si3, except for the spin-glass transition at 8 K inheriting from Tb2NiSi3. This new spin-glass transition in Tb2Ni0.8Mn0.2Si3 is absent in Tb2NiSi3. It takes place below the long-range magnetic ordered phase transition and shows cluster spin glass behaviors, and it is attributed to the introduction of Mn ions into the intermetallic compound.

Heisenberg Spin Chains via Chalcogen Bonding: Noncovalent S···O Contacts Enable Long-Range Magnetic Order.

The new radical ligand 5,8-dimethyl-1,4-dioxonaphtho[2,3-d][1,2,3]dithiazolyl (1) is reported. Two crystal polymorphs, 1α and 1β, differing in their pancake-bonded dimerization motif and S···O contact network, are identified. The self-assembly of Mn(II) metal ions with 1 leads to the formation of [Mn(hfac)2]3(1)2 that exhibits a Mn(II)-radical-Mn(II)-radical-Mn(II) linear arrangement of three Mn(hfac)2 units bridged by two radical ligands (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato-). Characterization by single-crystal X-ray diffraction of this Mn(II) complex packing structure reveals close noncovalent S···O contacts between the [Mn(hfac)2]3(1)2 units in one dimension along the b-c direction. The magnetic properties of the coordination complex are characterized by dc and ac susceptibility measurements on a microcrystalline solid. The magnetic data down to 4.8 K indicate the presence of effective ferromagnetic interactions (J/kB = +0.16 K) between the molecular ST = 13/2 units along the supramolecular chain involving noncovalent S···O contacts. Below 2.9 K, a non-zero out-of-phase component appears in the ac susceptibility, indicating the presence of a three-dimensional magnetic phase transition.

Study of the magnetic properties of YbMn2Sb2 single crystals by [formula omitted]SR

The crystal growth and the structural, transport and magnetic properties of YbMn2Sb2 single crystals are reported. The crystals show a trigonal symmetry of La2O2S-type structure (space group P3¯m1, N. 164, hP5), where corrugated honeycomb layers of MnSb are separated by Yb atoms. No structural phase transition was observed down to 22 K. The resistivity measurements show a predominantly insulating behavior. The combined resistivity, dc susceptibility and specific heat measurements confirm successive features at 40 K, 116 K and 225 K, being the phase transition at TN=116 K due to the Mn+2 lattice antiferromagnetic ordering. Muon spin rotation experiments (μSR) reveal a more complicated scenario, with temperature dependence of the magnetic volume fraction reflecting a static and strongly disordered magnetic ground state. The role of spin–lattice coupling and its relationship with exchange interactions between Mn moments is discussed as a possible cause of the magnetic behavior observed.

Magnetic structure investigation of the intercalated transition metal dichalcogenide V1/3NbS2

We investigate the temperature evolution of the magnetic structure of ${\mathrm{V}}_{1/3}{\mathrm{NbS}}_{2}$ using neutron diffraction techniques. We find that ${\mathrm{V}}_{1/3}{\mathrm{NbS}}_{2}$ has two propagation vectors: ${\mathbf{k}}_{\mathbf{0}}=(0,0,0)$ and ${\mathbf{k}}_{\mathbf{1}}=(0,0,\frac{1}{3})$. The ${\mathbf{k}}_{\mathbf{0}}$ vector can be associated with an antiferromagnetic ordering of in-plane moments with a refined value of $0.90(5){\ensuremath{\mu}}_{\mathrm{B}}$, and ${\mathbf{k}}_{\mathbf{1}}$ can be associated with moments along the $c$ axis in an up-down-down configuration with refined values of $1.21(12){\ensuremath{\mu}}_{\mathrm{B}}$ and $0.61(6){\ensuremath{\mu}}_{\mathrm{B}}$. Both ${\mathbf{k}}_{\mathbf{0}}$ and ${\mathbf{k}}_{\mathbf{1}}$ magnetic components couple with an out-of-plane ferromagnetic moment consistent with magnetization data. Furthermore, single-crystal neutron diffraction shows evidence of diffuse magnetic scattering between the (010) and ($01\ifmmode\pm\else\textpm\fi{}\frac{1}{3}$) Bragg peaks. We also characterize the field and temperature evolution of the magnetic structure in ${\mathrm{V}}_{1/3}{\mathrm{NbS}}_{2}$ by magnetic susceptibility and heat capacity measurements. The dc susceptibility measurements give an antiferromagnetic transition temperature of ${T}_{\mathrm{N}}=50$ K, and the field scans reveal that the moment does not saturate at magnetic fields up to 100 kOe.

Double magnetic phase transitions and magnetotransport anomalies in a new compound Gd2AgSi3

Dc and ac–magnetic susceptibility (χ), specific heat (CP), electrical resistivity (ρ) and magnetoresistance measurements performed on the new polycrystalline compound Gd2AgSi3, crystallizing in the α–ThSi2 tetragonal structure, are reported. Two magnetic phase transitions were observed in dc and ac susceptibility, specific heat and resistivity measurements at temperatures TN1=11 K and TN2=20 K, despite a single site occupied by Gd atom, which is an indication of the complex magnetic behavior. Gd2AgSi3 turns out be one of the rare Gd compound in which a minimum is observed in the temperature dependence of resistivity in the paramagnetic state and also negative magnetoresistance over a wide temperature range (above TN2), mimicking the behavior of exotic Gd2PdSi3, in this ternary family. The isothermal magnetic entropy change, adiabatic temperature change, and refrigerant capacity reach a value of 9.5 J/kg-K, 7.5 K and 302 J/kg, respectively for the change of magnetic field 0-9 T.

Linear shaped hetero-metallic [Zn2Ln4] clusters with Schiff base ligand: Synthesis, characterization and magnetic properties

A series of isostructural 3d–4f coordination clusters (CCs) [Zn2Ln4(L1)4(L2)2(OAc)2(N3)2] [Na2(OH2)2(NO3)3.2(N3)0.8]∙2MeCN, where Ln = Dy (1), Ho (2), Er (3), Tm (4), and Yb (5), L1 = 6-Methoxy-2-(2-pyridylmethyliminomethyl)phenol and L2 = (E)-2-methoxy-6-(2-((3-methoxy-2-oxidobenzylidene)amino)-1-oxido-2-(pyridin-2-yl)ethyl)phenolate has been synthesised and structurally characterised. The magnetic properties of 1–5 have been investigated using dc and ac susceptibility measurements. The paramagnetic metal ions within the clusters are weakly antiferromagnetically coupled, with the Er and Dy compounds displaying slow relaxation of their magnetisation. This is the first report of this versatile ligand being used to target 3d–4f coordination clusters.

Néel ordering in the distorted honeycomb pyrosilicate: C–Er2Si2O7

The rare-earth pyrosilicate family of compounds (RE2Si2O7) hosts a variety of polymorphs, some with honeycomb-like geometries of the rare-earth sublattices, and the magnetism has yet to be deeply explored in many of the cases. Here we report on the ground state properties of C–Er2Si2O7. C–Er2Si2O7 crystallizes in the C2/m space group and the Er3+ atoms form a distorted honeycomb lattice in the a–b plane. We have utilized specific heat, DC susceptibility, and neutron diffraction measurements to characterize C–Er2Si2O7. Our specific heat and DC susceptibility measurements show signatures of antiferromagnetic ordering at 2.3 K. Neutron powder diffraction confirms this transition temperature and the relative intensities of the magnetic Bragg peaks are consistent with a collinear Néel state in the magnetic space group C2’/m, with ordered moment of 6.61 μ B canted 13° away from the c-axis toward the a-axis. These results are discussed in relation to the isostructural quantum dimer magnet compound Yb2Si2O7.

Heterometallic Group 4-Lanthanide Oxo-alkoxide Precursors for Synthesis of Binary Oxide Nanomaterials.

In this study, an efficient procedure for the synthesis of uncommon group 4-lanthanide oxo-alkoxide derivatives was developed. Heterometallic clusters with the structures [La2Ti4(μ4-O)2(μ3-OEt)2(μ-OEt)8(OEt)6(Cl)2(HOEt)2] (1), [La2Zr2(μ3-O)(μ-OEt)5(μ-Cl)(OEt)2(HOEt)4(Cl)4]n (2), [La2Hf2(μ3-O)(μ-OEt)5(μ-Cl)(OEt)2(HOEt)4(Cl)4]n (3), [Nd2Ti4(μ4-O)2(μ3-OEt)2(μ-OEt)8(OEt)6(HOEt)2(Cl)2] (4), [Nd4Zr4(μ3-O)2(μ-OEt)10(μ-Cl)4(OEt)8(HOEt)10(Cl)2] (5), and [Nd4Hf4(μ3-O)2(μ-OEt)10(μ-Cl)4(OEt)8(HOEt)10(Cl)2] (6) were synthesized via the reaction of a metallocene dichloride, Cp2M'Cl2 (where M' = Ti, Zr, and Hf), and metallic lanthanum or neodymium in the presence of excess ethanol. This procedure gave crystalline precursors with molecular stoichiometries suitable for obtaining group 4-lanthanide oxide materials. Compounds 1-6 were examined by analytical and spectroscopic techniques and single-crystal X-ray diffraction. The magnetic properties of 5 and 6 were investigated by using direct and alternating current (dc and ac) susceptibility measurements. The results indicated weak antiferromagnetic interactions between NdIII ions and a field-supported slow magnetic relaxation. Lanthanum-titanium compound 1 decomposed at 950 °C to give the perovskite compound La0.66TiO3 and small amounts of rutile TiO2. Under the same conditions, 4 decomposed to give a mixture of Nd4Ti9O24 and Nd0.66TiO3. When 4 was calcined at 1300 °C, decomposition of Nd4Ti9O24 to Nd0.66TiO3 and TiO2 was observed. Calcination of 2, 3, 5, and 6 at 950-1500 °C led to the selective formation of heterometallic La2Zr2O7, La2Hf2O7, Nd2Zr2O7, and Nd2Hf2O7 phases, respectively.

Structure changes from radical-3d ring dimer to radical-3d-4f 1D chain with different magnetic properties

An unreported nitronyl nitroxide radical ligand and its corresponding radical-4f (complexes 1–3) and radical-3d-4f complexes (complexes 4–6) were successfully prepared. Structural analyses indicate that the complexes 1–3 are cyclic structures consist of two identical units of Ln(hfac)3(NIT-5-OCH3-3pyridine) (hfac = hexafluoroacetylacetone; Ln = Gd 1, Tb 2, Dy 3), while the complexes 4–6 show 1D zigzag structures with periodic [Rad–Ln–Rad–Cu] (Ln = Gd 4, Tb 5, Dy 6) units. Dc susceptibility measurements reveal that two different magnetic interactions coexist in complex 1: (i) ferromagnetic coupling between Gd3+ and radical through the NO group, (ii) weak antiferromagnetic interaction between Gd3+ and radical through the pyridine ring. While for complex 4, weak ferromagnetic coupling between Cu2+/Ln3+ and radical ligands as well as antiferromagnetic coupling between two adjacent radicals via the Ln3+ are observed at the same time. Furthermore, AC magnetic studies reveal that complexes 2, 3 and 5 display slow magnetization relaxation at low-temperature.

Respuesta ferrimagnética-antiferromagnéticasintonizable mediante la inclusión de Fe en la manganita basada en gadolinio GdMnO3

In this work a study of the synthesis process, crystal structure and magnetic behavior of gadolinium manganite with Fe substitutions in Mn positions of GdMn1-xFexO3(x=0, 0.1, 0.2) is reported. The samples were synthetized by the conventional solid-state reaction method. Structural characterization of final compounds was analyzed by Rietveld refinement, which revealed its crystallization in an orthorhombic symmetry belonging to the Pbnm (No. 62) space group. Results reveal that aand ccell parameters and the unit cell volume increase, while the lattice parameter band the cell volume decrease with Fe substitution. The main effect in the structure is related to oxygen positions, i.e. in the octahedral distortions and rotations. DC susceptibility measurements, in the temperature regime between 4 K and 300 K on the application of an external field of 200 Oe, show a paramagnetic feature at high temperatures for all xstudied values, with magnetic transitions associated to a magnetic ordered state at low temperatures (21.8 K &lt; T &lt; 25.2 K). Meanwhile, a ferrimagnetic transition is detected for x=0.1close to T=30.7 K.In order to explain the appearance of ferrimagnetism for this configuration, a model is suggested where an imbalance in the magnetic structure of GdMnO3(type-Aantiferromagnetic) generated due to the introducing a Fe3+ion in each pair consecutive unit cells is proposed. Theeffective magnetic moment obtained agrees to the reported value for the material with x=0.0, confirming the ferrimagnetic behavior for this concentration of Fe3+in the structure.

Synthesis, characterization and magnetic studies of dinuclear lanthanide complexes constructed with a Schiff base ligand

A series of seven isostructural homometallic dinuclear lanthanide metal complexes having the general formula [Ln2(L)2(NO3)4]·2CH3 OH, where L = 6-methoxy-2-(2-pyridylmethyliminomethyl) phenol Ln = Tb (1), Dy (2), Ho (3), Er (4), Tm (5), Yb (6), and Lu (7), are described. Compounds 1–7 were obtained from the reactions of Schiff base ligand (L) with the respective metal nitrates in the presence of triethylamine in MeOH. The structure of 2 was determined by single-crystal X-ray diffraction and the remaining compounds were characterized from X-ray powder diffraction patterns and found to be isostructural. The magnetic properties of 1–7 have been investigated using dc and ac susceptibility measurements. All these compounds show antiferromagnetic behavior between adjacent paramagnetic centers. Out of these seven compounds, only 2 displays an out-of-phase ac susceptibility signal which is attributed to the presence of the anisotropic DyIII ions.

Reentrant spin-glass behaviour in highly frustrated Mn-rich spinel zinc manganate

The present work offers an insight into the magnetic properties of Mn-rich spinel zinc manganate. Rietveld refinement reveals the formation of Zn0.67Mn2.33O4, where Zn2+ and Mn2+ ions are randomly distributed in the tetrahedral sublattice. DC and AC susceptibility measurement of Zn0.67Mn2.33O4 infers the occurrence of two kinds of transition below 11 K. Paramagnetic to ferrimagnetic transition occur at 10.7 K and ferrimagnetic to spin glass-like transition occurs at 5.8 K. The long-range canted ferrimagnetic ordering is corroborated using modified Lotgering model and calculated the exchange interaction values (JAA = 5.2 K,JAB = 5.3 K, JBB = 14.8 K). Further, the observed shift in freezing temperature with DC magnetic field obeys Almeida–Thouless behaviour and frequency dependence of AC susceptibility follows Vogel–Fulcher law. However, the complete establishment of the canonical spin glass state is denied since the manganese ions occupied at the tetrahedral site is equal to the percolation threshold (=33%). Subsequently, the observed spin glass-like behaviour (5.8 K) below Curie temperature (10.7 K) evidences the reentrant spin glass nature. Similarly, the strong frustration in Zn0.67Mn2.33O4 lattice is observed through the substantial negative value of Curie–Weiss temperature (∼−599 K) and very high frustration factor (f = 56). Overall, the chosen Zn0.67Mn2.33O4 is a highly frustrated magnetic system revealing re-entrant spin-glass behaviour.