Positive zero-field splitting and unexpected slow magnetic relaxation in the magneto-chemical calibrant HgCo(NCS)4

Magnetochemical standard HgCo(NCS)4 with positive zero-field splitting parameter D displays a slow magnetic relaxation strongly dependent upon the external magnetic field.

Observation of strong helical excitons and unexpectedly giant Rashba splitting in single crystal two-dimensional Organic-Inorganic Halide Perovskites

Two-dimensional (2D) organic-inorganic lead halide perovskites possess strong spin-orbit coupling, and in the presence of broken inversion symmetry, this may lead to helical excitons and Rashba splitting at the band extrema1-6. However, a direct and systematic measurement of the helical excitons and the Rashba parameter in the system is still lacking. Here, we report distinct two bright co-helical and two dark anti-helical excitons in single crystal ((CH3(CH2)3NH3)2(CH3NH3)n-1PbnI3n+1 (n = 1 to 4), where n determines quantum well (QW) thickness of inorganic layer7. By comprehensively analyzing the fine structure of helical excitons, we find that the Rashba splitting originates from surface inversion asymmetry and surface-normal electric fields, which are determined by the QW’s dielectric environment, n and temperature. The Rashba splitting parameter is found among the highest recorded of 2.66 and 2.5 eV∙Å for the conduction and valence band of n=1 Iodide, respectively, and reduces for n>1 Iodide. Our result shows the importance of helical excitons and Rashba splitting and presents a direct method to quantify the Rashba parameter in complex halide perovskites. We hope that our study inspires applications of QW materials in novel spintronic devices.

Correlating magnetic anisotropy with the subtle coordination geometry variation of a series of cobalt(ii)-sulfonamide complexes

The distortion degree from the ideal tetrahedral geometry has been correlated with the zero-field splitting parameter in a series of mononuclear cobalt(ii)-sulfonamide complexes with a CoN4 coordination environment.

The stannides REIr2Sn4 (RE=La, Ce, Pr, Nd, Sm)

The stannides REIr2Sn4 (RE=La, Ce, Pr, Nd, Sm) were synthesized from the elements by arc melting or by induction melting in sealed niobium containers. They crystallize with the NdRh2Sn4 type structure, space group Pnma. The samples were characterized by powder X-ray diffraction (Guinier technique). Three structures were refined from single-crystal X-ray data: a=1844.5(2), b=450.33(4), c=716.90(6) pm, wR2=0.0323, 1172 F2 values, 44 variables for LaIr2Sn4, a=1840.08(2), b=448.24(4), c=719.6(1) pm, wR2=0.0215, 1265 F2 values, 45 variables for Ce1.13Ir2Sn3.87, and a=1880.7(1), b=446.2(1), c=733.0(1) pm, wR2=0.0845, 836 F2 values, 45 variables for Ce1.68Ir2Sn3.32. The structures consist of three-dimensional [Ir2Sn4] polyanionic networks in which the rare earth atoms fill pentagonal prismatic channels. The striking structural motif concerns the formation of solid solutions RE1+xIr2Sn4−x on the Sn4 sites, which have similar coordination as the RE sites. Temperature dependent magnetic susceptibility measurements revealed diamagnetic behavior for LaIr2Sn4. CeIr2Sn4, PrIr2Sn4 and NdIr2Sn4 show Curie-Weiss paramagnetism while SmIr2Sn4 exhibits typical van Vleck paramagnetism. Antiferromagnetic ground states were observed for CeIr2Sn4 (TN=3.3 K) and SmIr2Sn4 (TN=3.8 K). 119Sn Mössbauer spectra show a close superposition of four sub-spectra which can be distinguished through their isomer shift and the quadrupole splitting parameter.

Structural and magnetic properties of Co(II) complexes with tridentate ONO pincer-type ligands

Pincer type ligand 2,6-pyridinedimethanol was used as a useful tool in the preparation of the Co(II) pseudoctahedral complex together with 3,5-dinitrobenzoate counteranion. New complex of the composition [Co(pydm)2](3,5-dnbz)2(pydm = 2,6-pyridinedimethanol, and 3,5-dnbz = 3,5-dinitrobenzoate anion) has been prepared and characterized. Its XRD structure revealed pseudooctahedral {CoN2O4} chromophore around the cobalt atom with Co-N distances significantly shorter (Co-Nav = 2.038 Ǻ) in comparison to the Co-O ones (Co-Oav = 2.142 Ǻ), which was probably the reason of its relatively high zero-field splitting parameter (D/hc = 43.6 cm-1). Positive value of the D parameter causes slow relaxation process typical for Co(II) SMM behavior. The 3,5-dinitrobenzoate counteranions are strongly bonded to the [Co(pydm)2] cation via rather strong hydrogen bonds (O∙∙∙Oav = 2.568 Ǻ) forming “quasi molecular” units. Solid state structure allowed different π-π stacking interactions of neighboring “molecular” unit aromatic rings probally leading to observation of the additional relaxation mode.

Quantitative analysis of zero-field splitting parameter distributions in Gd(iii) complexes

The Zero-Field Splitting (ZFS) distributions in Gd(iii) centers are accurately analyzed, with detailed discussion of error bars, and compared to the calculations with superposition model.

Abnormal Magnetic Moment and Zero Field Splitting of Some Nickel (II) Complexes

<em>Some complexes of Ni(II) have been prepared with 2-thio-3-acetyl hydantoin (TAHN) and 2-formyl pyridine thiosemicarbazone (FPTS). On the basis of elemental analysis and molar conductivity, the complexes have been formulated as NiL₂X₂, where L = TAHN or FPTS and X = Cl^–, Br^–, NCS^–, ClO₄^–. The infrared spectra of complexes and free ligand reveal that the ligand TAHN is co-ordinated through sulphur and acetyl oxygen, while FPTS ligand co-ordinates through heterocyclic nitrogen and sulphur to Ni(II) metal ion. The magnetic moment of these complexes are found to be 3.20-3.25 B.M. The values are greater than value (2.828 B.M) corresponding to two unpaired electrons of a d⁸-system. The appearance of four absorption bands in their electronic spectra reveal, the tetragonal distortion in the octahedral symmetry of complexes. The zero field splitting parameter(D) and the other crystal field parameters like Dq_(xy), Dq_(z), Dt have been calculated. The results show that, the tetragonal distortion parameter (Dt) increases in the order of NCS^–&lt; Cl^– &lt; Br^– while the zero field splitting parameter (D) also increases in the same order for both the planer ligands.</em>

Probing the influence of molecular symmetry on the magnetic anisotropy of octahedral cobalt(ii) complexes

A series of field-induced cobalt(ii) SIMs exhibit varying axial zero-field splitting parameter D values from positive to negative with the increased distortion of the octahedral geometry.