Fitting Of Magnetic Data Research Articles

SquidLab-A user-friendly program for background subtraction and fitting of magnetization data.

We present an open-source program free to download for academic use with a full user-friendly graphical interface for performing flexible and robust background subtraction and dipole fitting on magnetization data. For magnetic samples with small moment sizes or sample environments with large or asymmetric magnetic backgrounds, it can become necessary to separate background and sample contributions to each measured raw voltage measurement before fitting the dipole signal to extract magnetic moments. Originally designed for use with pressure cells on a Quantum Design MPMS3 SQUID magnetometer, SquidLab is a modular object-oriented platform implemented in Matlab with a range of importers for different widely available magnetometer systems (including MPMS, MPMS-XL, MPMS-IQuantum, MPMS3, and S700X models) and has been tested with a broad variety of background and signal types. The software allows background subtraction of baseline signals, signal preprocessing, and performing fits to dipole data using Levenberg-Marquardt non-linear least squares or a singular value decomposition linear algebra algorithm that excels at picking out noisy or weak dipole signals. A plugin system allows users to easily extend the built-in functionality with their own importers, processes, or fitting algorithms. SquidLab can be downloaded, under Academic License, from the University of Warwick depository (wrap.warwick.ac.uk/129665).

Structural and Magnetic Properties of Six-Line Ferrihydrite Nanoparticles

Magnetic properties of antiferromagnetic nanoparticles are not as straight forward as for ferromagnetic and ferrimagnetic nanoparticles. We analyzed the data of antiferromagnetic six-line ferrihydrite nanoparticles by considering distribution in particle magnetic moment. The fit of magnetization data, using non-linear least square fit procedure, considering Langevin function with and without distribution in particle magnetic moment, is presented. Magnetization of the system is measured as function of temperature and applied magnetic field.

Magnetic properties and critical behavior of electron doped polycrystalline Ca0.85Sm0.15MnO3 manganite

We have reported the magnetic properties and critical behavior of electron doped Ca0.85Sm0.15MnO3 (CSMO) sample prepared by solid state reaction technique. With increasing temperature the CSMO sample undergoes ferromagnetic to paramagnetic phase transition at 115 K. The positive value of the Landau coefficient b(T) estimated from the fitting of magnetization data with equation of state suggests that the CSMO sample undergoes 2nd order magnetic phase transition. The positive slopes of Arrott plots corroborate the same. Further study of the critical behavior of the CSMO sample was done by analysis of Kouvel–Fisher plot and critical isotherm. The calculated values of the critical exponents and differ significantly from the values which correspond to three dimensional mean field, tri-critical mean field, 3D Ising and 3D Heisenberg models. This indicates the nonconventional nature of ferromagnetism induced in the CSMO sample by Sm doping at the Ca site.

Structure and Magnetic Properties of a New Lattice System of the Heterometallic Decanuclear Ce6Mn4 Aggregate

In this paper, we present a mixed valence f–d Ce6Mn 4 III compound having formula [Ce 6 IV Mn 4 III (μ4-O)4 (μ3-O)4(O2CtBu)12(ea)4(OAc)4]·H2O (1), which is obtained by the reaction of hydrated lanthanide nitrate, pivalic acid, and ethanolamine in MeCN as a solvent. The single crystal X-ray diffraction analysis demonstrates that the central core consists of an octahedron with four triangular pyramids added to four related faces or as an octahedron encapsulated in a tetragon. The fitting of magnetization data using the anisotropic model gives D = 2.13 cm–1 and g = 1.97 (D is the axial zero-field splitting parameter).

Synthesis and magnetic properties of a 1-D helical chain derived from a Nickel-Sodium Schiff base complex

The reaction of the deprotonated form of the Schiff base ligand; (E)-2-methoxy-6-((phenylimino) methyl)phenol (L) with nickel chloride hydrate results in the formation of the 1-dimentional coordination polymer; Na[Ni(L)2(OMe)(MeOH)]n (1). The structure was determined via single crystal X-ray diffraction measurements. A careful analysis of the complex shows that the polymer exists as a helical structure, where the helicity is brought about by the presence of an alkali metal ion which is observed for the first time. Moreover the helical structure in 1 is maintained predominantly through covalent bond rather than supramolecular interactions. Direct current magnetic susceptibility measurement suggests that complex 1 obeys the Curie law. The fitting of magnetic data using the PHI software package yields parameters of S = 1, g = 2.26 and D = +4.51 (or D = −7.24 cm−1) for 1. We report a 1-D helical chain of Nickel Schiff base complexes whose helicity is brought by a sodium ion in the crystal lattice. Preliminary magnetic behavior suggests that there is no super-exchange interaction between the nickel ions via a closed shell sodium ion.

Utilization of the Spin Symmetry in Fitting the Magnetic Data lor Large Exchange Clusters

Abstract The Heisenberg Hamiltonian appropriate to exchange clusters commutes with the square of the total spin ant its third component. Therefore in studying the exchange coupled clusters of medium/high nuclearity the spin quantum number S can be utilized in factoring of large interaction matrices (dimension of which is 104 - 105). Then the blocks of much lower size can be diagonalized using the desktop computers. To this end, the eigenvalues form the partition function Z(T,B) from which all thermodynamic properties, including the magnetization M(B,T0) and the magnetic susceptibility χ(T,B0), can be reconstructed. The matrix elements of the interaction operators in the coupled basis set of spin kets have been generated with the help of the irreducible tensor operators for a loop for S = Smin until S = Smax. In addition to the modelling of energy levels for different topologies, a fitting of magnetic data is exemplified by a number of examples like [Fe6] and [Mn3Cr4] systems

Family of Double-Cubane Mn4Ln2 (Ln = Gd, Tb, Dy, Ho) and Mn4Y2 Complexes: A New Mn4Tb2 Single-Molecule Magnet

The synthesis and characterization of a family of Mn(2)(III)Mn(2)(II)Ln(III)(2) complexes (Ln = Gd (1), Tb (2), Dy (3), and Ho (4)) of formula [Mn(4)Ln(2)O(2)(O(2)CBu(t))(6)(edteH(2))(2)(NO(3))(2)] are reported, where edteH(4) is N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine. The analogous Mn(4)Y(2) (5) complex has also been prepared. They were obtained from reaction of Ln(NO(3))(3) or Y(NO(3))(3) with Mn(O(2)CBu(t))(2), edteH(4), and NEt(3) in a 2:3:1:2 molar ratio. The crystal structures of representative 1 and 2 were obtained, and their core consists of a face-fused double-cubane [Mn(4)Ln(2)(μ(4)-O(2-))(2)(μ(3)-OR)(4)] unit. Such double-cubane units are extremely rare in 3d metal chemistry and unprecedented in 3d-4f chemistry. Variable-temperature, solid-state dc and ac magnetic susceptibility studies on 1-5 were carried out. Fitting of dc χ(M)T vs T data for 5 gave J(bb) (Mn(III)···Mn(III)) = -32.6(9) cm(-1), J(wb) (Mn(II)···Mn(III)) = +0.5(2) cm(-1), and g = 1.96(1), indicating a |n, 0, n> (n = 0-5) 6-fold-degenerate ground state. The data for 1 indicate an S = 12 ground state, confirmed by fitting of magnetization data, which gave S = 12, D = 0.00(1) cm(-1), and g = 1.93(1) (D is the axial zero-field splitting parameter). This ground state identifies the Mn(II)···Gd(III) interactions to be ferromagnetic. The ac susceptibility data independently confirmed the conclusions about 1 and 5 and revealed that 2 displays slow relaxation of the magnetization vector for the Mn(4)Tb(2) analogue 2. The latter was confirmed as a single-molecule magnet by observation of hysteresis below 0.9 K in magnetization vs dc field scans on a single crystal of 2·MeCN on a micro-SQUID apparatus. The hysteresis loops also displayed well-resolved quantum tunneling of magnetization steps, only the second 3d-4f SMM to do so.

Diruthenium Compounds Bearing Equatorial Fc-containing Ligands: Synthesis and Electronic Structure

Previously, the synthesis of compounds Ru(2)(D(3,5-Cl(2)Ph)F)(4-n)(O(2)CFc)(n)Cl (n = 1, 3a; 2, 4a), where D(3,5-Cl(2)Ph)F is N,N'-di(3,5-dichlorophenyl)formamidinate, from the carboxylate exchange reactions between Ru(2)(D(3,5-Cl(2)Ph)F)(4-n)(OAc)(n)Cl and ferrocene carboxylic acid was communicated. Reported herein is the preparation of analogous compounds Ru(2)(DmAniF)(4-n)(O(2)CFc)(n)Cl (n = 1, 3b; 2, 4b), where DmAniF is N,N'-di(3-methoxyphenyl)formamidinate, from Ru(2)(DmAniF)(4-n)(OAc)(n)Cl. Compounds 3 and 4 were characterized with various techniques including X-ray structural determinations of 3a and 4a. Voltammetric behaviors of compounds 3 and 4 were investigated, and stepwise one-electron ferrocene oxidations were observed for both compounds 4a and 4b. Spectral analysis of the monocations [4](+) indicated that they are the Robin-Day class II mixed valent [Fc···Fc](+) species. Measurement and fitting of magnetic data (χT) of 4a between 2 and 300 K revealed a typical zero-field splitting of a S = 3/2 center with D = 77 cm(-1), while those of [4a]BF(4) are consistent with the presence of S = 3/2 (Ru(2)) and S = 1/2 (Fc(+)) centers that are weakly coupled (zJ = -0.76 cm(-1)).

Two New μ‐(1,3‐Azido)‐Bridged Polymers: Alternating Single and Double Bridges in a 1D Nickel(II) Complex and Uniform Bridge in a 2D Copper(II) Complex: Syntheses, Single‐Crystal Structures and Magnetic Studies

AbstractTwo polymeric azido bridged complexes [Ni2L2(N3)3]n(ClO4)n (1) and [Cu(bpds)2(N3)]n(ClO4)n(H2O)2.5n (2) [L = Schiff base, obtained from the condensation of pyridine‐2‐aldehyde with N,N,2,2‐tetramethyl‐1,3‐propanediamine; bpds = 4,4'‐bipyridyl disulfide] have been synthesized and their crystal structures have been determined. Complex 1, C26H42ClN15Ni2O4, crystallizes in a triclinic system, space group P$\tilde {1}$ with a = 8.089(13), b = 9.392(14), c = 12.267(18) Å, α = 107.28(1), β = 95.95(1), γ = 96.92(1)° and Z = 2; complex 2, C20H21ClCuN7O6.5S4, crystallizes in an orthorhombic system, space group Pnna with a = 10.839(14), b = 13.208(17), c = 19.75(2) Å and Z = 4. The crystal structure of 1 consists of 1D polymers of nickel(L) units, alternatively connected by single and double bridging μ‐(1,3‐N3) ligand with isolated perchlorate anions. Variable temperature magnetic susceptibility data of the complex have been measured and the fitting of magnetic data was carried out applying the Borrás‐Almenar formula for such types of alternating one‐dimensional S = 1 systems, based on the Hamiltonian H = –JΣ(S2iS2i–1 + αS2iS2i+1). The best‐fit parameters obtained are J =–106.7 ± 2 cm–1; α = 0.82 ± 0.02; g = 2.21 ± 0.02. Complex 2 is a 2D network of 4,4 topology with the nodes occupied by the CuII ions, and the edges formed by single azide and double bpds connectors. The perchlorate anions are located between pairs of bpds. The magnetic data have been fitted considering the complex as a pseudo‐one‐dimensional system, with all copper(II) atoms linked by μ(1,3‐azido) bridging ligands at axial positions (long Cu···N3 distances) since the coupling through long bpds is almost nil. The best‐fit parameters obtained with this model are J = –1.21 ± 0.2 cm–1, g = 2.14 ± 0.02. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Synthesis, Structure and Magnetic Properties of a Series of Novel Isophthalate‐Bridged Manganese(II) Polymers with Double‐Layer or Double‐Chain Structures

AbstractFour isophthalate‐bridged manganese(II) coordination polymers, [Mn4(ip)4(H2O)2(Him)4]n (1), [Mn(ip)(Him)2]n (2), [Mn(ip)(dpe)]n·0.5ndpe·nH2O (3) and [Mn2(ip)2(bpy)2]n (4) [ip = isophthalate, Him = imidazole, bpy = 2,2′‐bipyridine and dpe = (E)‐1,2‐bis(4‐pyridyl)ethene], have been rationally synthesized and characterized by single‐crystal X‐ray structure determinations and magnetic studies. Both 1 and 3 are two‐dimensional (2D) double‐layer polymers. In 1, novel Mn4 entities are linked by ip ligands, while 3 is made of [Mn(ip)]n parallel double chains cross‐linked by the μ‐dpe ligands. Both 2 and 4 are one‐dimensional (1D) double‐chain polymers, where 2 is composed of [Mn(ip)]n parallel double chains capped by the Him ligands, while 4 is made of [Mn2(ip)2]n helical double chains capped by the chelating bpy ligands. Variable‐temperature magnetic susceptibility measurements revealed weak antiferromagnetic exchange interactions between the adjacent MnII ions of the four coordination polymers. The data of 2−4 were fitted to the homonuclear alternating chain model to give magnetic coupling parameters of J1 = −0.71(4) to −1.01(3) cm−1 and J2 = −0.02(2) to −0.46(2) cm−1. In the case of 1, the fitting of magnetic data considering only the interactions within the Mn4 moiety led to J = −2.17(1) cm−1 and zJ′ = −0.01(5) cm−1, using a combination of a dimeric model and a mean molecular field approximation model. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The first one-dimensional manganese polymer containing 4,5-dicarboxyimidazole: solvothermal synthesis, crystal structure and magnetic behavior of [Mn(phen)(Hdcbi)]n (H3dcbi=4,5-dicarboxyimidazole, phen=1,10-phenanthroline)

Solvothermal reaction of Mn(OAc)2·4H2O with 4,5-dicarboxyimidazole and phenanthroline resulted in a complex [Mn(phen)(Hdcbi)]n1 in which Hdcbi as a μ2-bridge links two neighboring manganese(II) ions in chelating mode, forming one-dimensional zigzag chain framework. The fitting of magnetic data (J=−0.11 cm−1, zJ′=−0.06 cm−1, g=2.01) indicates weak antiferromagnetic coupling interactions between the Mn(II) sites.