Field Dependence Of Magnetic Susceptibility Research Articles

Tomonaga-Luttinger liquid and quantum criticality in spin- antiferromagnetic Heisenberg chain C 14 H 18 CuN 4 O 10 via Wilson ratio.

The ground state of a one-dimensional spin- uniform antiferromagnetic Heisenberg chain (AfHc) is a Tomonaga-Luttinger liquid which is quantum-critical with respect to applied magnetic fields up to a saturation field beyond which it transforms to a fully polarized state. Wilson ratio has been predicted to be a good indicator for demarcating these phases [Phys. Rev. B 96, 220401 (2017)]. From detailed temperature and magnetic field-dependent magnetization, magnetic susceptibility and specific heat measurements in a metalorganic complex and comparisons with field theory and quantum transfer matrix method calculations, the complex was found to be a very good realization of a spin- AfHc. Wilson ratio obtained from experimentally obtained magnetic susceptibility and magnetic contribution of specific heat values was used to map the magnetic phase diagram of the uniform spin- AfHc over large regions of phase space demarcating Tomonaga-Luttinger liquid, saturation field quantum critical, and fully polarized states. Luttinger parameter and spinon velocity were found to match very well with the values predicted from conformal field theory.

Novel Trinuclear Copper(II) Complex: Crystal Structure at 100 K and Magnetic Properties of (R, S)-di[(6,7-dimethoxy-isoquinolin-1-yl)-(3,4-dimethoxy-phenyl)-methanolato]-tetra(2-hydroxybenzoato)-diaqua-tricopper dihydrate, [Cu3(C7H5O3)4(C20H20NO5)2(H2O)2]·2(H2O)

The crystal structure of [Cu3(C7H5O3)4(C20H20NO5)2(H2O)2]·2(H2O) (1) and analysis of temperature and field dependence of magnetic susceptibility is reported in this work. The structure of 1 is composed of trinuclear complex units and water molecules. The middle copper atom occupies the center of symmetry. N, O-bonded (6,7-dimethoxy-isoquinolin-1-yl)-(3,4-di­methoxy-phenyl)-methanolato ligands, 2-hydroxybenzoates with bridging carboxylic groups, and oxo-bridged water molecules connect the middle Cu(II) atom with the terminal copper atoms. Two 2-hydroxybenzoates coordinate the terminal copper atoms via one carboxylic oxygen and an O atom of the hydroxyl group. The analysis of copper coordination by bond-valence sum approach and relevant structural correlation is consistent with hexacoordinated Cu(II) centers. Cu···Cu separation is 3.0269(3) Å. The magnetism of 1 shows a strong ferromagnetic interaction between the neighboring metallic centers accompanied by very weak antiferromagnetic intermolecular interactions. The complex units are mutually held by π···π stack interactions of 2-hydroxybenzoates and hydrogen bonds.Graphical A new N,O bonded ligands, (R, S)-[(6,7-dimethoxy-isoquinolin-1-yl)-(3,4-dimethoxy-phenyl)-methanolate] coordinate the terminal atoms of the trinuclear copper(II) complex.

Spin canting and slow magnetic relaxation in mononuclear cobalt(II) sulfadiazine ternary complexes.

Monomeric [Co(SDZ)2phen] (1) and [Co(SDZ)(bq)Cl] (2) complexes (SDZ = sulfadiazine, phen = 1,10-phenanthroline, and bq = 2,2'-biquinoline) have been synthesized and characterized. X-ray diffraction studies indicate that SDZ acts as a bidentate ligand coordinating through the sulfonamide and the pyrimidine N atoms in both compounds. In complex 1, the coordination sphere consists of two SDZ ligands and a bis-chelating phen ligand, giving rise to a CoN6 coordination sphere. On the other hand, 2 has a CoN4Cl core, with two N-atoms from SDZ and two from the bq ligand. Both compounds have been studied by dc and ac magnetometry and shown to display slow magnetic relaxation under an optimum external dc field (1 kOe) at low temperatures. Moreover, compound 2 displays long range magnetic ordering provided by spin-canted antiferromagnetism, which has been characterized by further field-dependent magnetic susceptibility measurements, FC/ZFC curves, hysteresis loops and frequency-independent ac curves. The signs of the calculated D parameters, positive in 1 and negative in 2, have been rationalized according to the two lowest-lying transitions in the orbital energy diagrams derived from ab initio ligand field theory (AILFT). In a subsequent attempt to reveal the possible hidden zero-field SMM behaviour, Ni(II)-based 3 and Co(II)-doped Ni(II)-based (with a Ni : Co ratio of 0.9 : 0.1) heterometallic compound 2Ni were synthesized.

Suppression of ferromagnetism in La3CrAs5 via V substitution

In this work, we successfully synthesized a series of hexagonal La3Cr1-xVxAs5 (x = 0–0.8) polycrystalline samples under high-temperature and high-pressure conditions. A systematic study was carried out via the measurements of X-ray powder diffraction, temperature- and field-dependent magnetic susceptibility and magnetization. The X-ray diffraction data show that the lattice constant. a-parameter gradually increases, while c-parameter decreases with increasing V-doping level. In this series, the ferromagnetic behavior has been observed for x ≤ 0.3, and the Curie temperature TC decreases from 50 K for the parent compound to 20 K for x = 0.3, which indicates that the ferromagnetism is suppressed as the V-doped increases. For x = 0.4, the system begins to enter into a new magnetic state like spin glass at low temperature, and no magnetic order can be observed down to 2 K for x ≥ 0.8. In addition, the Weiss temperature Tϴ gradually decreases and changes to be negative for x = 0.6, which suggests that ferromagnetic interaction at first is weakened by the V substitution, and then transforms into anti-magnetic predominant interaction. The above results indicate that there is no quantum criticality occurred in the La3Cr1-xVxAs5 system.

Tunable Magnetic Transition Temperatures in Organic–Inorganic Hybrid Cobalt Chloride Hexagonal Perovskites

Magnetically active atomic distances may impact the magnetic ordering in a given system both directly and indirectly. We synthesize three novel quasi-one-dimensional organic–inorganic hybrid cobalt chloride chain compounds (CH3NH3CoCl3, CH(NH2)2CoCl3, and C(NH2)3CoCl3) and characterize their magnetic and thermodynamic properties. These materials crystallize in a hexagonal perovskite-type structure consisting of chains of face-sharing Co–Cl octahedra separated by the respective organic cation. Temperature- and field-dependent magnetic susceptibility analyses reveal that each compound possesses antiferromagnetic intrachain coupling and that the strength of the correlations is comparable across the three materials. Moreover, the interchain Co–Co distance, which depends on the size of the organic cation, is directly related to the temperature at which long-range magnetic ordering occurs.

Honeycomb oxide heterostructure as a candidate host for a Kitaev quantum spin liquid

Kitaev quantum spin liquid, massively quantum entangled states, is so scarce in nature that searching for new candidate systems remains a great challenge. Honeycomb heterostructure could be a promising route to realize and utilize such an exotic quantum phase by providing additional controllability of Hamiltonian and device compatibility, respectively. Here, we provide epitaxial honeycomb oxide thin film Na3Co2SbO6, a candidate of Kitaev quantum spin liquid proposed recently. We found a spin glass and antiferromagnetic ground states depending on Na stoichiometry, signifying not only the importance of Na vacancy control but also strong frustration in Na3Co2SbO6. Despite its classical ground state, the field-dependent magnetic susceptibility shows remarkable scaling collapse with a single critical exponent, which can be interpreted as evidence of quantum criticality. Its electronic ground state and derived spin Hamiltonian from spectroscopies are consistent with the predicted Kitaev model. Our work provides a unique route to the realization and utilization of Kitaev quantum spin liquid.

Curie Temperatures and Emplacement Conditions of Pyroclastic Deposits From Popocatépetl Volcano, Mexico

AbstractMost pyroclastic deposits of Popocatépetl volcano were emplaced at high temperatures and have similar mafic to more evolved compositions, suggesting a long‐lived, interconnected magma environment. We performed a magnetic and microscopic study on different eruptive sequences <14 ky in age and found that temperature and field dependence of magnetic susceptibility are suited to separate eruption phases. We observed homogeneous titanomagnetite with Curie temperatures (TC) of 50–200°C and 200–400°C, together with different amounts of oxy‐exsolved titanomagnetite with TC ∼ 570°C. Some block‐and‐ash flow deposits show remarkably irreversible TC in heating and cooling branches with a positive ΔTC (TC heating–TC cooling) of up to 130°C in the center. The central part of this sequence is characterized by decreasing magnetic susceptibility and low field dependence of magnetic susceptibility (<10%), which is atypical for ulvöspinel‐rich titanomagnetite. The nonreversibility of heating and cooling runs measured with rates of around 10 K/min is probably related to vacancy‐enhanced nanoscale chemical clustering, which seems to occur preferentially during rapid quenching, possibly combined with subtle maghemitization. In contrast, pumice layers have the highest field dependence (∼20%) and contain Ti‐rich and intermediate titanomagnetite with TC < 100 and ∼300°C, which are in line with mafic and more evolved magma composition. In intermediate phases, irreversibility of TC is more common but with a relatively low ΔTC of ±20°C. We suggest that magneto‐mineralogy in pyroclastic density currents is complex but offers a complementary tool to the paleomagnetic directional analysis for emplacement temperature and contribute information on the volcanic material history and their emplacement conditions.

Metamagnetic phase transition in the ferromagnetic superconductor URhGe

Ferromagnetic superconductor URhGe has orthorhombic structure and possesses spontaneous magnetisation along the c-axis. Magnetic field directed along the $b$-axis suppresses ferromagnetism in $c$-direction and leads to a metamagnetic transition into polarised paramagnetic state in the $b$-direction. The theory of these phenomena based on the specific magnetic anisotropy of this material in $(b,c)$ plane is given. Line of the first order metamagnetic transition ends at a critical point. The Van der Waals - type description of behaviour of physical properties near this point is developed. The triplet superconducting state destroyed by orbital effect is recreated in vicinity of the transition. It is shown that the reentrance of superconductivity is caused by the sharp increase of magnetic susceptibility in $b$ direction near the metamagnetic transition. The specific behaviour of the upper critical field in direction of spontaneous magnetisation in UCoGe and in UGe$_2$ related to the field dependence of magnetic susceptibility is discussed.

Magnon and spin transition contribution in heat capacity of ferromagnetic Cr-doped MnTe: Experimental evidence for a paramagnetic spin-caloritronic effect

We present experimental evidence for the simultaneous existence of the magnons and spin-state transition contributions to the heat capacity in ferromagnetic (FM) Cr-doped MnTe (Tc ∼ 280 K), where the magnon heat capacity is attributed to the observed magnon-bipolar carrier-drag thermopower. The pristine antiferromagnetic (AFM) MnTe shows only a magnon-induced peak in the heat capacity near the Néel temperature, TN ∼ 307 K. However, Cr-doped MnTe shows a magnon-contributed heat capacity peak at ∼293 K with an additional peak in the deep paramagnetic domain near 780 K. Temperature-dependent magnetic susceptibility reveals that Cr-doping initially creates low-spin (LS) state Mn2+ ions into MnTe near and below TN due to a higher crystal field induced by Cr ions. Above 400 K, LS Mn2+ ions start converting into high-spin (HS) Mn2+ ions. The LS-to-HS transition of Mn2+ leads to an excess entropy and hence excess heat capacity contribution in the system. Temperature-dependent X-ray diffraction (XRD) and magnetic field-dependent susceptibility (M-H) confirmed no presence of any structural changes and magnetic polaron, respectively. Both XRD and M-H ensure that the peak of the heat capacity in the paramagnetic domain is originated solely by the spin-state transition. The heat capacity vs temperature was calculated to explain the contribution of each component, including the ones due to the phonons, magnons, spin-transition, Schottky anomaly, and lattice dilation. With the recent advances in spin-caloritronics extending the spin-based effects from magnetic to paramagnetic materials, the data from the heat capacity can play a crucial role to probe the presence of different phenomena, such as paramagnon-carrier-drag and spin-entropy thermopowers.

Magnetic field-induced metamagnetic, magnetocaloric and pyrocurrent behaviors of Eu2CoMnO6

In this paper, the structural, transport, pyrocurrent and magnetic behaviors of Eu2CoMnO6 (ECMO) sample are reported. It was prepared by the solid-state reaction method and crystallized in monoclinic crystal structure with a space group of P21/n. A systematic study of the temperature and magnetic field-dependent susceptibility revealed a complex magnetic behavior with field-induced type-II metamagnetic phase transition of the first-order. The multiple sharp jumps in the initial magnetization curve for T < 10 K could be attributed to structural distortion related to the martensite-like strains from E*-type antiferromagnetic to ferromagnetic ordering. The metastable magnetic behavior for T ≥ 60 K is ascribed to a transformation of the low-field disordered spin glass phase to long-range ordered ferromagnetic phase, induced by critical fields. These critical fields are quite sensitive to the direction and magnitude of the field-cooling process. The temperature-dependent magnetocaloric effect with maximum value of ~3.3 J kg−1K−1 at TC ~ 123 K and the electrical transport behavior of ECMO were studied. Further, temperature dependent pyroelectric current and polarization data of ECMO are investigated.

Doping Method Determines Para- or Superparamagnetic Properties of Photostable and Surface-Modifiable Quantum Dots for Multimodal Bioimaging

Semiconductor quantum dots (QDs) are widely used for optical applications and bioimaging. In comparison to organic dyes used for fluorescent labeling, QDs exhibit very high photostability and can be further surface modified. Equipping QDs with magnetic properties (mQDs) makes it possible to combine fluorescence and magnetic resonance imaging analyses. For this purpose, we have prepared water-dispersible and magnetic CdTe/ZnS mQDs, whereby ferrous ions are selectively incorporated in either their cores or their shells. This study aims at understanding the differences in optical, structural, and magnetic properties between these core- and shell-doped mQDs. Field-dependent isothermal magnetic susceptibility measurements show that shell-doped mQDs exhibit paramagnetic and their core-doped equivalents superparamagnetic behavior near room temperature. Shell doping results in about 1.7 times higher photoluminescence quantum yields and 1.4 times higher doping efficiency than core doping. X-ray diffraction pattern...

Fluorescigenic Magnetofluids Based on Gadolinium, Terbium, and Dysprosium-Containing Imidazolium Salts.

Multistimuli responsive soft materials are urgently needed in many different fields, such as anticounterfeiting technology and microdroplet manipulation. Herein, the straightforward preparation of fluorescigenic magnetofluids by the introduction of the paramagnetic metal ions Gd3+, Tb3+, and Dy3+ into alkylimidazolium-based ionic liquids (ILs) is reported. Bright visible fluorescence was observed under UV irradiation for Tb- and Dy-containing ILs. Either pure samples or papers coated with these ILs exhibited pronounced magnetic responses. Consistent and stable structures of these salts were confirmed by systematical characterizations. Because of the competition of nitrate ligands, structural water in the precursors was eliminated easily under a vacuum. For Tb- and Dy-containing ILs, featured electronic transitions were observed and were assigned in the fluorescence spectra. The long lifetimes of these transitions were also confirmed. The field-cooling experiments showed that all of these ILs display paramagnetism at room temperature. At low temperature, small deviations from the Curie Law indicate the occurrence of antiferromagnetic coupling and spin canting in these ILs. Temperature-induced differences in magnetic properties were further verified by field-dependent magnetic susceptibility measurements carried out at 5 and 300 K.

Negative Oxygen Isotope Effect in Manganites with an Ordered Cation Arrangement in a High Magnetic Field

The oxygen isotope effect in PrBaMn216-18 O5.97 manganite with an ordered cation arrangement is studied. The field dependences of magnetic susceptibility and magnetization are measured in the temperature range 100–270 K and magnetic fields up to 32 T. A significant increase in the temperature of the spin-reorientation antiferromagnet–ferromagnet phase transition is detected in samples enriched in heavy oxygen 18O (negative isotope effect). The transition temperature and the isotope effect depend strongly on the magnetic field. An H–T phase diagram is plotted for samples with various isotope compositions. An analysis of the experimental results demonstrates that the detected negative isotope effect and the giant positive isotope effect revealed earlier in doped manganites have the same nature. The mechanisms of appearance of isotope effects are discussed in terms of the double exchange model under a polaron narrowing of the free carrier band.

Hyperfine-Interaction-Driven Suppression of Quantum Tunneling at Zero Field in a Holmium(III) Single-Ion Magnet.

An extremely rare non-Kramers holmium(III) single-ion magnet (SIM) is reported to be stabilized in the pentagonal-bipyramidal geometry by a phosphine oxide with a high energy barrier of 237(4) cm-1 . The suppression of the quantum tunneling of magnetization (QTM) at zero field and the hyperfine structures originating from field-induced QTMs can be observed even from the field-dependent alternating-current magnetic susceptibility in addition to single-crystal hysteresis loops. These dramatic dynamics were attributed to the combination of the favorable crystal-field environment and the hyperfine interactions arising from 165 Ho (I=7/2) with a natural abundance of 100 %.

Nontrivial Recurrent Intergrowth Structure and Unusual Magnetic Behavior of Intermetallic Compound Fe32+δGe33As2.

A new phase Fe32+δGe33As2 (δ ≤ 0.136) was obtained by two-step synthesis from the elements. Fe32+δGe33As2 crystallizes in its own structure type (space group P6/mmm, Z = 1, a = 11.919(3) Å, c = 7.558(4) Å) that can be described as a recurrent two-dimensional intergrowth of two intermetallic structure types, MgFe6Ge6 and Co2Al5. Their blocks are represented by infinite columns in the structure. No visible structural changes were observed in the temperature range from 10 to 300 K. At 125 K, Fe32+δGe33As2 undergoes an antiferromagnetic-like transition, while above 150 K it shows a typical Curie-Weiss paramagnetic behavior. Below the transition temperature, a peculiar field-dependent magnetic susceptibility, that shows a significant increase of the susceptibility upon increasing the magnetic field, and a change in transport properties have been observed. Above 140 K, Fe32+δGe33As2 reveals a metallic behavior, in agreement with electronic structure calculation, while below this point the resistivity nonmonotonically increases upon cooling. The Seebeck coefficient is positive, indicating that holes are the major charge carriers, and shows a broad maximum around 57 K.

Experimental investigations of thermal stability of some morpholinecarbamic acid complexes of copper(II) and zinc(II)

Some new carbamates, viz. M(MorphcbmH)2X2 (MorphcbmH = morpholinecarbamic acid, M = Cu, X = Cl, ClO4,NO3; M = Zn, X = Cl, ClO4, NO3, CH3COO and X2 = SO4), have been synthesized and investigated. Compounds were characterized by elemental analysis, molar conductance, FT infrared, fluorescence, NMR (1H and 13C) and solution electronic absorption spectral studies. Room temperature field-dependent magnetic susceptibility measurements, PXRD spectral and cyclic voltametric studies were also conducted. Chelating bidentate mode of coordination of ligand, MorphcbmH with four coordination around metal ion has been proposed. Ligand and its compounds have also been studied using non-isothermal thermogravimetric analysis and differential scanning calorimetric analytical techniques which inferred formation of metal oxide/MCO3 as final thermal decomposition products. Compounds were screened against the lipase enzyme for assaying their enzyme activity and were found to retard the lipase activity from 48.16 to 0.044 µmol mL−1 min−1.

Time solved susceptibility spectra of magnetic fluids

Measurements of the frequency (f) and polarizing field (H) dependent complex magnetic susceptibility, χ(f, H)=χ′(f, H)–iχ″(f, H) of a magnetic fluid over the frequency range 1kHz to 2MHz, in various polarizing fields from zero to approximately 7kA/m are presented. The sample was a commercial magnetic fluid with magnetite particles in isopar-M.Usually, Brownian relaxation time measurements are involved in the investigation of particle agglomeration in magnetic fluids. In some situations the presence of miscellaneous particles may induce erroneous conclusions. The paper shows that over time measurements can solve the problem in giving confirmation of particle agglomeration within magnetic fluids. Measurements performed in a constant polarizing field of, H=7kA/m, have shown that after 30min both components of the complex magnetic susceptibility increased and the relaxation peak shifted towards higher frequencies. The phenomenon is correlated to the particle aggregation process and demonstrates that the relaxation peaks are due to the rotation of small aggregates.

A thioether-decorated {Mn11Tb4} coordination cluster with slow magnetic relaxation

A {MnIII11TbIII4}-nuclearity coordination complex with structurally exposed thioether functional groups and antiferromagnetic intramolecular coupling interactions was synthesised and characterised by temperature- and field-dependent magnetic susceptibility measurements.

Suppression of ferromagnetism in the La(VxCr1−x)Sb3 system

To explore the possibility of quantum phase transitions and even quantum criticality in LaCrSb based compounds, we performed measurements under pressure as well as a vanadium substitution study. The Curie temperature of LaCrSb was found to be invariant under pressure. Although pressure was not able to suppress the ferromagnetism, chemical substitution was used as another parameter to tune the magnetism. We grew La(VCr)Sb (x = 0–1.0) single crystals and studied the series by measurements of temperature- and field-dependent magnetic susceptibility, magnetization, resistivity and specific heat. Ferromagnetism has been observed for , and the system manifests a strong anisotropy in its ordered state. The Curie temperature decreases monotonically as the V concentration increases. For , the system enters a new magnetic state at low temperatures, and no magnetic ordering above 1.8 K can be observed for . The effective moment /Cr varies only slightly as the V concentration increases, from 3.9 for = 0 to 2.9 for = 0.88. Features related to quantum criticality have not been observed in the La(VCr)Sb system.

Anisotropic magnetic properties and crystal electric field studies on CePd2Ge2 single crystal

The anisotropic magnetic properties of the antiferromagnetic compound CePd2Ge2, crystallizing in the tetragonal crystal structure have been investigated in detail on a single crystal grown by the Czochralski method. From the electrical transport, magnetization and heat capacity data, the Néel temperature is confirmed to be 5.1 K. Anisotropic behaviour of the magnetization and resistivity is observed along the two principal crystallographic directions—namely, [100] and [001]. The isothermal magnetization measured in the magnetically ordered state at 2 K exhibits a spin reorientation at 13.5 T for the field applied along the [100] direction, whereas the magnetization is linear along the [001] direction attaining a value of 0.94 μB/Ce at 14 T. The reduced value of the magnetization is attributed to the crystalline electric field (CEF) effects. A sharp jump in the specific heat at the magnetic ordering temperature is observed. After subtracting the phononic contribution, the jump in the heat capacity amounts to 12.5 J K−1mol−1 which is the expected value for a spin system. From the CEF analysis of the magnetization data the excited crystal field split energy levels were estimated to be at 120 K and 230 K respectively, which quantitatively explains the observed Schottky anomaly in the heat capacity. A magnetic phase diagram has been constructed based on the field dependence of magnetic susceptibility and the heat capacity data.