Ac Magnetic Susceptibility Measurements Research Articles

The effect of the outer-sphere cations on the photophysical and magnetic properties of rare earth complexes with 2,2,2-trichloro-N-(diphenylphosphoryl)acetamide

Two series of rare earth coordination compounds have been synthesized (Na[RE(L4)] (labeled as 1RE) and PPh4[RE(L4)] (labeled as 2RE), where RE = Y3+, Eu3+, Tb3+, L = 2,2,2-trichloro-N-(diphenylphosphoryl)acetamide) to determine the possibility of modifying their photophysical and magnetical properties by changing the counterion. The crystal structure of 1RE was determined based on the single-crystal X-ray diffraction and the crystal structure of 2RE was determined based on quantum chemistry computational procedures. Characterization of the physicochemical properties of the compounds was carried out using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), 1H and 31P NMR spectroscopy as well as FT-IR, absorption and luminescence spectroscopy in the temperature range of 300 - 77 K. The rate constants of radiative (Arad) and non-radiative (Anrad) transitions, intrinsic (QLnLn) and overall (QLnL) emission quantum yields, sensitization efficiency (ηsens), the experimental and theoretical intensity parameters (Ωλ), the forward (WS, WT) and backward (WbS, WbT) intramolecular energy transfer (IET) rates were determined. Magnetic properties of Tb3+ compounds were studied in a constant field of 0.5 T in the temperature range of 1.8–300 K. Dynamic AC magnetic susceptibility measurements were carried out as a function of temperature and frequency for 1Tb and 2Tb. Only in the case of 2Tb, in the presence of an external DC field, a slight temperature dependence of in-phase χ′ and out-of-phase χ'' susceptibility was recorded. Based on experimental and theoretical results, the significant effect of counterion on the photophysical and magnetic properties of RE chelates has been demonstrated and clarified, providing valuable guidance for the design of bifunctional electromagnetic radiation converters.

Magnetic short-range order and Griffiths-like phase in the S-1/2 spin-dimer ferromagnet BaCu(SeO3)2

The polycrystals of S = 1/2 spin-dimer compound BaCu(SeO3)2 have been synthesized by using solid-state reaction. Without long-range order, the magnetic susceptibility χ(T) curve presents two anomalies at T1 = 5 K and TG = 58 K due to antiferromagnetic (AFM) short-range order and short-range ferromagnetic (FM) correlations, respectively, which is further supported by the specific heat and electron spin resonance data. The high-temperature χ(T) curve follows the Curie-Weiss law with θCW = 11.3 K, showing the dominant intradimer FM interaction. The magnetization M(H) curve at 2 K is characteristic of an AFM-FM transition at 0.4 T, suggesting the weak interdimer AFM couplings. The density function theory calculations and quantum Monte Carlo simulations allow an estimation of the intradimer and interdimer exchanges with J1/kB = 39.09 K, J2/kB = −1.51 K, and J3/kB = −1.68 K. Interestingly, the χ−1(T) curve within θCW <T <TG deviates downward from paramagnetic Curie-Weiss behavior, mimicking the Griffiths-like phase. This is further supported by the ac magnetic susceptibility and magnetic relaxation measurements. The competing intradimer FM and interdimer AFM exchanges with a subtle ratio between them are proposed to be responsible for the formation of Griffiths-like phase.

Spin-Cluster Glassy and Long-Range Ordered Magnetic States in Honeycomb-Layered Compositionally Complex Oxides Na3-xLixT2SbO6 (T = Cu1/3Ni1/3Co1/3).

The concept of high-entropy oxides has triggered extensive research of this novel class of materials because their numerous functional properties are usually not mere linear combinations of those of the components. Here, we introduce the new series of compositionally complex honeycomb-layered magnets Na3-xLixT2SbO6 (T = Cu1/3Ni1/3Co1/3). An unusual feature of the system is its nonmonotonous dependences of the monoclinic lattice parameters b and β on x. Rietveld refinement of the crystal structures of the Na and Li end members reveals apparent Sb-T site inversion in the former and considerable Li-Cu site inversion in the latter. The materials are characterized by measurements of specific heat Cp, magnetization M, and ac and dc magnetic susceptibility χ. Na3T2SbO6 exhibits sharp long-range antiferromagnetic order (TN = 10.2 K) preceded by noticeable correlation effects at elevated temperatures. The magnetic phase diagram of Na3T2SbO6 is established. Introduction of Li, just at x = 0.8, destroys AFM order, resulting in spin-cluster glass behavior attributed to Li/Cu inversion, with TG growing with x to 10.4 K at x = 3.

Synthesis, crystal structure and magnetic properties of two 1D coordination polymers containing Co2+ and Cu2+ ions and 1,3,5-tris(4-carboxylphenyl)benzene

Two 1D coordination polymers, {[Co(H3BTB)2(phen)](NO3)2}n (1) and {[Cu(HBTB)2(phen)] DMF}n (2), were synthesized through a slow diffusion reaction between the metal ions Co2+ or Cu2+, 1,3,5-tris(4-carboxylphenyl)benzene (H3BTB) and 1,10-phenanthroline (phen). Single-crystal X-ray diffraction revealed that both metal centers are involved in a distorted octahedral environment. As expected for a Cu2+ ion with a d9 configuration, a pronounced Jahn-Teller distortion is observed. FTIR, powder XRD, and thermogravimetric analysis were employed for the chemical characterization of the two complexes. CASSCF-NEVPT2 was used to calculate the axial magnetic anisotropy (D) for complex 1, and the results were almost perfectly consistent with the experimental measurements. The AC magnetic susceptibility measurements revealed field-induced single-ion magnet (SIM) behavior at low temperatures for 1. EPR studies of complex 2 indicated that the Cu2+ ions are essentially isolated.

A Gadolinium(III) Complex Based on Pyridoxine Molecule with Single-Ion Magnet and Magnetic Resonance Imaging Properties.

Pyridoxine (pyr) is a versatile molecule that forms part of the family of B vitamins. It is used to treat and prevent vitamin B6 deficiency and certain types of metabolic disorders. Moreover, the pyridoxine molecule has been investigated as a suitable ligand toward metal ions. Nevertheless, the study of the magnetic properties of metal complexes containing lanthanide(III) ions and this biomolecule is unexplored. We have synthesized and characterized a novel pyridoxine-based GdIII complex of formula [GdIII(pyr)2(H2O)4]Cl3 · 2 H2O (1) [pyr = pyridoxine]. 1 crystallizes in the triclinic system and space group Pī. In its crystal packing, cationic [Gd(pyr)2(H2O)4]3+ entities are connected through H-bonding interactions involving non-coordinating water molecules and chloride anions. In addition, Hirshfeld surfaces of 1 were calculated to further investigate their intermolecular interactions in the crystal lattice. Our investigation of the magnetic properties of 1, through ac magnetic susceptibility measurements, reveals the occurrence of a slow relaxation in magnetization in this mononuclear GdIII complex, indicating an unusual single-ion magnet (SIM) behavior for this pseudo-isotropic metal ion at very low temperatures. We also studied the relaxometric properties of 1, as a potential contrast agent for high-field magnetic resonance imaging (MRI), from solutions of 1 prepared in physiological serum (0.0-3.2 mM range) and measured at 3 T on a clinical MRI scanner. The values of relaxivity obtained for 1 are larger than those of some commercial MRI contrast agents based on mononuclear GdIII systems.

The effect of the gelation temperature on the structural, magnetic and magnetocaloric properties of perovskite nanoparticles manufactured using the sol-gel method.

This study presents a comprehensive investigation of the structural and magnetic properties of La0.8Sr0.2Mn0.8Co0.2O3 (LS1, LS2 and LS3) compounds synthesized via the sol-gel method at different gelation temperatures through X-ray diffraction and different magnetic measurement techniques. The Rietveld refinement demonstrated that all samples exhibit a rhombohedral perovskite structure with the R3̄C space group. Their magnetic behavior, characterized through magnetization measurements, hysteresis loops, and Arrot plots, demonstrates a ferromagnetic-paramagnetic transition with notable soft ferromagnetic characteristics. The samples also demonstrate second-order magnetic transitions, short-range magnetic order and the presence of both ferromagnetic and antiferromagnetic contributions. AC magnetic susceptibility measurements, allowing the investigation of the magnetic dynamics of the samples, shows that the Vogel-Fulcher and the Conventional Critical Slowing Down models are the most appropriate for describing the dynamic behavior, confirming the spin-glass nature of the compounds and the presence of medium to strong interaction between magnetic nanoparticles. The influence of gelation temperature in the magnetocaloric effect of the compounds was proven and LS1, synthesized at the lowest gelation temperature (70 °C), exhibits the higher magnetic entropy change (|ΔSmax| = 3.25 J kg-1 K-1 and RCP = 209.83 J kg-1 at 5 T). For a better evaluation of the magnetocaloric efficiency, the temperature average entropy change (TEC) parameter was calculated for all three samples and LS1 showed the highest value (TEC (LS1) ∼3.2 J kg-1 K-1 for ΔTH-C = 10 K and ΔH = 5 T).

High-Pressure Synthesis, Crystal Structure, and Physical Properties of a Spinel Compound Co0.7Al2S4.

In this paper, we report on the discovery of a spinel compound, Co0.7Al2S4, which was synthesized at high-pressure. The systematic characterizations were carried out by structural, magnetic, and heat capacity measurements. The compound crystallizes into a cubic structure with the space group Fd3̅m (no. 227) and the lattice constant a = 9.9580(1) Å. Magnetic susceptibility measurements suggest that Co0.7Al2S4 exhibits a spin glass ground state, freezing at Tf ∼ 7.2 K with a Weiss temperature Tθ ∼ -115.9 K, which is verified by ac magnetic susceptibility and heat capacity measurements. The frustration parameter f for Co0.7Al2S4 is calculated to be about 16.6, based on the formula f = | Tθ/Tf |, indicating that Co0.7Al2S4 is a high-frustration magnet. Specific heat data displays a T2 dependence below the freezing temperature, which is different from the linear dependence observed in a common spin glass system. Compared with the similar compound CoAl2O4, it is suggested that the vacancies in the Co sites should be responsible for the occurrence of the spin glass behavior of Co0.7Al2S4.

Magnetic ac susceptibility of superconducting Ta films for quantum computing

Recently, breakthroughs were reported in the long coherence time (>0.5 ms) transmon qubit using tantalum films (Ta). Identifying the loss mechanism in Ta films will help further improve the performance of Ta-based superconducting qubits. Here, we report a study of superconducting properties in two sets of Ta films grown on c-cut and a-cut sapphires respectively using contact transport and noncontact magnetic ac susceptibility measurements. Although the resistive transition appears to be similar in both films, we found strikingly different responses in their complex magnetic susceptibilities . in the c-cut films exhibits a sharp peak at superconducting transition T c and becomes featureless below T c indicating a strongly coupled superconducting state. In contrast, in the a-cut films exhibits a broad peak near T c and a second peak appears below T c, indicating granular superconductivity behavior. This second peak in is associated with the hysteresis loss at weak-link-type grain boundaries, which is believed to be a leading source of decoherence in the a-cut Ta films. The derived magnetic loss tangent in the a-cut films is about one order of magnitude higher than in the c-cut films. This study demonstrates that ac susceptibility is an excellent probe for characterizing bulk superconducting properties of the constituent superconducting materials used in qubits.

Structure and properties of NdCuGa[formula omitted] single crystals

This manuscript reports on the structural and magnetic properties of NdCuGa3 using powder and single crystal X-ray diffraction (XRD), zero-field single crystal neutron diffraction, magnetization, and specific heat measurements. Our XRD on a single crystal specimen of NdCuGa3 confirmed that it crystallizes in the tetragonal BaNiSi3-type structure. A magnetic phase transition at TN= 3.3 K is assessed using specific heat and ac magnetic susceptibility measurements. No additional anomaly below TN down to 50 mK was detected by performing specific heat measurements. Neutron single crystal diffraction data collected at T= 300 mK confirm the antiferromagnetic phase below TN= 3.3 K with the propagation vector τ→= (0.2, 0, 0). Possible magnetic structure solutions of NdCuGa3 are discussed.

Emergence of field-induced memory effect in spin ices

Out-of-equilibrium investigation of strongly correlated materials deciphers the hidden equilibrium properties. Herein, we have investigated the out-of-equilibrium magnetic properties of polycrystalline Dy2Ti2O7 and Ho2Ti2O7 spin ices. Our experimental findings reveal the emergence of magnetic field-induced anomalous hysteresis observed solely in temperature-and magnetic field-dependent AC susceptibility measurements. The observed memory effect (anomalous thermomagnetic hysteresis) exhibits a strong dependence on both thermal and non-thermal driving variables. Owing to the non-collinear spin structure, the applied DC bias magnetic field produces quenched disorder sites in the cooperative Ising spin matrix and suppresses the spin–phonon coupling. These quench disorders create a dynamic spin correlation, having slow spin relaxation and quick decay time, which additionally contribute to AC susceptibility. The initial conditions and measurement protocol decide the magnitude and sign of this dynamical term contributing to AC susceptibility. It is being suggested that such out-of-equilibrium properties arise from the combined influences of geometric frustration, disorder, and the cooperative nature of spin dynamics exhibited by these materials.

In-plane uniaxial-strain tuning of superconductivity and charge-density wave in CsV3Sb5

The kagome superconductor CsV3Sb5 with exotic electronic properties has attracted substantial research interest, and the interplay between the superconductivity and the charge-density wave is crucial for understanding its unusual electronic ground state. In this work, we performed resistivity and AC magnetic susceptibility measurements on CsV3Sb5 single crystals uniaxially-strained along [100] and [110] directions. We find that the uniaxial-strain tuning effect of T c (dT c/dε) and T CDW (dT CDW/dε) are almost identical along these distinct high-symmetry directions. These findings suggest the in-plane uniaxial-strain-tuning of T c and T CDW in CsV3Sb5 are dominated by associated c-axis strain, whereas the response to purely in-plane strains is likely small.

Superconducting spin reorientation in spin-triplet multiple superconducting phases of UTe2.

Superconducting (SC) state has spin and orbital degrees of freedom, and spin-triplet superconductivity shows multiple SC phases because of the presence of these degrees of freedom. However, the observation of spin-direction rotation occurring inside the SC state (SC spin rotation) has hardly been reported. Uranium ditelluride, a recently found topological superconductor, exhibits various SC phases under pressure: SC state at ambient pressure (SC1), high-temperature SC state above 0.5 gigapascal (SC2), and low-temperature SC state above 0.5 gigapascal (SC3). We performed nuclear magnetic resonance (NMR) and ac susceptibility measurements on a single-crystal uranium ditelluride. The b axis spin susceptibility remains unchanged in SC2, unlike in SC1, and decreases below the SC2-SC3 transition with spin modulation. These unique properties in SC3 arise from the coexistence of two SC order parameters. Our NMR results confirm spin-triplet superconductivity with SC spin parallel to b axis in SC2 and unveil the remaining of spin degrees of freedom in SC uranium ditelluride.

Cluster spin glass in off-stoichiometric Ni2.01Mn1.58Sn0.41 alloy

The Ni2.01Mn1.58Sn0.41 alloy is a member of the Heusler material family which undergoes diffusionless structural transition from cubic austenite to orthorhombic martensite during its cooling. The transition was observed at temperature 398 K from paramagnetic austenite to martensite with complex magnetic structure. The measurement of AC magnetic susceptibility of the alloy confirmed spin-glass state at temperatures below 155 K and from the frequency dependence of the cups in AC susceptibility, a presence of clusters (11 nm3 in size) with strong interaction is deduced. The alloy shows anomalous Hall effect (AHE) of the order of 0.051 μΩ cm at 2 K in the spin-glass state of the alloy and its sign changes at around 140 K. The ordinary Hall coefficient of the metallic alloy is strikingly positive in the whole studied temperature region, and it points to complex magnetic and electronic structure of the alloy. The electrical resistance of the sample shows a flat maximum of 220 μΩ cm at spin-glass transition temperature. The magnetoresistance is of the order of 1% and is negative in the whole temperature region which points to a standard scattering of charge carriers on magnetic fluctuations. Quantum-mechanical calculations of supercells with compositions Ni32Mn25Sn7, Ni32Mn26Sn6 and Ni32Mn24Sn8 simulated different arrangement of Mn and Sn atoms. Ni32Mn25Sn7 composition is thermodynamically the most stable, although its magnetic moment is 1.67 μB/f.u., twice higher than the measured value. The combination of the latter two states, with additional Mn–Sn swaps, provides the magnetic moments matching the experimental value at a very small energy cost. Theoretical results then indicate that a scenario of local chemical variations and clustering is likely in the studied alloy.

Field-Induced Single-Ion Magnet Behavior in Nickel(II) Complexes with Functionalized 2,2':6'-2″-Terpyridine Derivatives: Preparation and Magneto-Structural Study.

Two mononuclear nickel(II) complexes of the formula [Ni(terpyCOOH)2](ClO4)2∙4H2O (1) and [Ni(terpyepy)2](ClO4)2 MeOH (2) [terpyCOOH = 4'-carboxyl-2,2':6',2″-terpyridine and terpyepy = 4'-[(2-pyridin-4-yl)ethynyl]-2,2':6',2″-terpyridine] have been prepared and their structures determined by single-crystal X-ray diffraction. Complexes 1 and 2 are mononuclear compounds, where the nickel(II) ions are six-coordinate by the six nitrogen atoms from two tridentate terpy moieties. The mean values of the equatorial Ni-N bond distances [2.11(1) and 2.12(1) Å for Ni(1) at 1 and 2, respectively, are somewhat longer than the axial ones [2.008(6) and 2.003(6) Å (1)/2.000(1) and 1.999(1) Å (2)]. The values of the shortest intermolecular nickel-nickel separation are 9.422(1) (1) and 8.901(1) Å (2). Variable-temperature (1.9-200 K) direct current (dc) magnetic susceptibility measurements on polycrystalline samples of 1 and 2 reveal a Curie law behavior in the high-temperature range, which corresponds to magnetically isolated spin triplets, the downturn of the χMT product at lower temperatures being due to zero-field splitting effects (D). Values of D equal to -6.0 (1) and -4.7 cm-1 (2) were obtained through the joint analysis of the magnetic susceptibility data and the field dependence of the magnetization. These results from magnetometry were supported by theoretical calculations. Alternating current (ac) magnetic susceptibility measurements of 1 and 2 in the temperature range 2.0-5.5 K show the occurrence of incipient out-phase signals under applied dc fields, a phenomenon that is characteristic of field-induced Single-Molecule Magnet (SMM) behavior, which herein concerns the 2 mononuclear nickel(II) complexes. This slow relaxation of the magnetization in 1 and 2 has its origin in the axial compression of the octahedral surrounding at their nickel(II) ions that leads to negative values of D. A combination of an Orbach and a direct mechanism accounts for the field-dependent relation phenomena in 1 and 2.

Lipoic Acid-Functionalized Hexanuclear Manganese(III) Nanomagnets Suitable for Surface Grafting.

Highly anisotropic single-molecule magnets (SMMs) have attracted much interest in the field of molecular magnetism because of their spin features and potential technological applications. Additionally, a great effort has been devoted to the functionalization of such molecule-based systems which are made with ligands containing functional groups suitable to connect SMMs to junction devices or to perform their grafting on surfaces of different substrates. We have synthesized and characterized two lipoic acid-functionalized and oxime-based Mn(III) compounds, of formula [Mn6(μ3-O)2(H2N-sao)6(lip)2(MeOH)6][Mn6(μ3-O)2(H2N-sao)6(cnph)2(MeOH)6]}·10MeOH (1) and [Mn6(μ3-O)2(H2N-sao)6(lip)2(EtOH)6]·EtOH·2H2O (2) [H2N-saoH2 = salicylamidoxime, lip = lipoate anion, cnph = 2-cyanophenolate anion]. Compound 1 crystallizes in the space group Pī of the triclinic system and 2 crystallizes in the space group C2/c of the monoclinic system. In the crystal, neighboring Mn6 entities are linked using non-coordinating solvent molecules, which are H-bonded to N atoms of -NH2 groups of amidoxime ligand. In addition, Hirshfeld surfaces of 1 and 2 were calculated to study the variety of intermolecular interactions and the different levels of importance that take place in their crystal lattice; this type of computed study is the first time performed on Mn6 complexes. The study of the magnetic properties of 1 and 2 through dc magnetic susceptibility measurements reveals the coexistence of ferromagnetic and antiferromagnetic exchange couplings between the Mn(III) metal ions in both compounds, the latter being the predominant magnetic interaction. A spin S = 4 value of the ground state was obtained using isotropic simulations of the experimental magnetic susceptibility data for both 1 and 2. Ac magnetic susceptibility measurements show features typical of slow relaxation of the magnetization in 1 and 2, which indicate that SMM behavior takes place in both compounds.

Field Induced Multiple Superconducting Phases in UTe_{2} along Hard Magnetic Axis.

The superconducting (SC) phase diagram in uranium ditelluride is explored under magnetic fields (H) along the hard magnetic b axis using a high-quality single crystal with T_{c}=2.1 K. Simultaneous electrical resistivity and ac magnetic susceptibility measurements discern low- and high-field SC (LFSC and HFSC, respectively) phases with contrasting field-angular dependence. Crystal quality increases the upper critical field of the LFSC phase, but the H^{*} of ∼15 T, at which the HFSC phase appears, is always the same through the various crystals. A phase boundary signature is also observed inside the LFSC phase near H^{*}, indicating an intermediate SC phase characterized by small flux pinning forces.

A tetranuclear Er(III)-based cluster with bifunctional properties: Efficient conversion of CO2 and slow magnetic relaxation behavior

A new Er4 cluster [Er4(NO3)2(acac)4(L)2(CH3OH)2]·2CH3CN (1) (H4L = (E)-2-(hydroxymethyl)-2-(((2-hydroxynaphthalen-1-yl)methylene)amino)propane-1,3-diol, and Hacac = acetylacetone) were synthesized by employing a polydentate Schiff-base ligand (H4L) and a β-diketonate co-ligand and further characterized structurally. Alternating current (ac) magnetic susceptibility measurements indicated that cluster 1 shows slow relaxation of magnetization behavior. More importantly, cluster 1 shows high catalytic activity of the cycloaddition reaction of CO2 and epichlorohydrin under mild conditions; and cluster 1 as heterogenous catalyst can be reused at least three times without any obvious loss in catalytic activity. It is worth mentioning that cluster 1 is a rare bifunctional Ln(III)-based material for both molecular based magnetic material and heterogenous catalyst.

Antisite disorder mediated exchange bias effect and spin-glass state in La[formula omitted]Sm[formula omitted]NiMnO[formula omitted

We report the synthesis of La2−xSmxNiMnO6 (x = 0, 0.1, 0.2) polycrystalline compounds through the sol–gel process using all-aqueous precursors. The influence of Sm-substitution on magnetic properties of La2−xSmxNiMnO6 (LSNMO) compounds are investigated through X-ray diffraction (XRD), dc-magnetization (Mdc), ac-magnetic susceptibility measurements, and Raman spectroscopy. XRD analysis confirms that the phase stability of LSNMO is improved significantly upon Sm-substitution as evident from a structural phase transformation of the compound from a biphasic (monoclinic + rhombohedral) into an aphasic (monoclinic) structure. The magnetic measurements indicate a formation of a metastable magnetic state with random ferromagnetic (FM) and antiferromagnetic (AFM) interactions below 100 K. The metastable spin configuration exhibits critical slow-down dynamics and memory effect that signifies a spin-glass (SG) state. The influence of Sm-doping reduces the Curie temperature (Tc) from 284 K → 245 K and enhances saturation magnetization (Ms). These findings are attributed to the combined effect of a reduced degree of antisite disorder upon the addition of Sm. A profound variation (45.5 → 72.9 K) in SG transition temperature (TSG) is also reported. Magnetization loops M(H) confirm the presence of an exchange bias (EB) effect that value suppressed prominently from 120 → 28 Oe upon Sm-substitution. The temperature-dependent magnetization M(T) and frequency-dependent ac-susceptibility χ[ω, T] are used to study the antisite-driven SG phase, spin relaxation dynamics, magnetic memory, and rejuvenation effect. Raman spectroscopy is employed to probe the degree of antisites disorder that reduces after Sm-addition. The phase stability, lower Tc, tunable Ms, and EB in the single-phase compound make LSNMO a potential candidate for its applications in realizing energy-efficient devices.

Thermal and magnetic properties of Cu4O(SeO3)3 composed by ferrimagnetic O2Cu6 units of edge-sharing OCu4 tetrahedra

Monoclinic Cu4O(SeO3)3 has been prepared hydrothermally with subsequent heating in evacuated silica tubes. It has been characterized in measurements of dc and ac magnetic susceptibility χ and specific heat Cp. The title compound orders magnetically at T1 = 13.2 K and evidences a pre-transitional anomaly at T2 = 17.2 K. In the range T1 < T < T2, the application of external magnetic field rapidly suppresses excessive magnetization of this intermediate phase, but the hump in specific heat appears. The magnetic system of the title compound is constituted by the layered network of isolated Cu atoms and O2Cu6 units composed by edge-sharing anion-centered OCu4 tetrahedra. First principles calculations provided values of both ferromagnetic and antiferromagnetic exchange interactions within O2Cu6 units J1 – J11 and J12 – J22, and antiferromagnetic intralayer J23 – J30 and interlayer J31 – J32 exchange interactions. Basing on signs and values of these interactions a magnetic model of monoclinic Cu4O(SeO3)3 is suggested.

Weak ferromagnetism at 48.5 K in rubidium-intercalated biphenyl

Aromatic hydrocarbon molecules with π-conjugated structure have great potential for the search of exotic states such as high temperature superconductivity and novel quantum magnetism. In this work, we found that high temperature weak ferromagnetism can be achieved by intercalating rubidium into the shortest poly(para-phenylene) molecule—biphenyl. Both dc and ac magnetic susceptibility measurements showed that the synthesized material exhibits a typical antiferromagnetic transition at 48.5 K, accompanying a ferromagnetic character in the magnetically ordered region. Combining theoretical calculations and Raman spectroscopic studies, it was found that the mole ratio between rubidium and biphenyl is 1:1, and the molecular magnetic moments are formed by transferring the Rb-5s electrons to the C-2p orbitals. The weak ferromagnetism is produced by intralayer spin-canted antiferromagnetic and interlayer ferromagnetic spin couplings. Our finding enriches the physicochemical functionality of biphenyl and opens a window for the search of π-electron organic magnets in poly(para-phenylene) molecules.