Magnetization steps of spin quartets

Liu, M. T.; Shapira, Y.; Haar, Ewout ter; Bindilatti, V.

doi:10.1103/physrevb.54.6457

Cited by 19 publications

(17 citation statements)

References 16 publications

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“…More advanced experimental methods of determining J include inelastic-neutron scattering, 6,7 and magnetization steps. [8][9][10][11][12][13] The last two techniques probe directly the energy-level structure. Besides yielding J, these two methods may reveal the presence of weak interactions in addition to the intramolecular-exchange interactions.…”

Section: Introductionmentioning

confidence: 99%

Magnetization steps in[Fe(salen)Cl]2

et al. 1999

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The differential susceptibility dM /dH of ͓Fe͑salen͒Cl͔ 2 where salen is N,NЈ-ethylenebis͑salicylideneiminato͒, was measured in pulsed magnetic fields up to 550 kOe. The samples were in a capsule that was immersed in a liquid-helium bath maintained at a temperature 1.5рT bath р4.2 K. Three magnetization steps ͑MST's͒ arising from energy-level crossings for the Fe 3ϩ dimer were observed as peaks in dM /dH. The intradimer exchange constant obtained from the MST's is JϭϪ8.4Ϯ0.2 cm Ϫ1 , assuming a g factor of 2.00. The line shapes of the peaks in dM /dH strongly suggest the existence of weak interactions that are not included in the conventional model of independent dimers with isotropic intradimer exchange only. The missing weak interactions are yet to be identified. The narrow widths of the peaks in dM /dH indicate strong departures from thermal equilibrium with the helium bath during the field pulse ͑milliseconds duration͒. Such narrow widths are the result of cooling by the magnetocaloric effect. The cooling, and therefore the line shapes of the dM /dH peaks, depended on the arrangement for the sample-to-bath heat flow during the field pulse. With one heat-flow arrangement hysteresis was observed. Computer simulations of the line shape resulting from the magnetocaloric effect during the field pulse reproduce the narrow widths and the hysteresis. Data for the low-field magnetic susceptibility between 2 and 300 K, measured in steady fields, gave JХϪ8 cm Ϫ1 .

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Section: Introductionmentioning

confidence: 99%

Magnetization steps in[Fe(salen)Cl]2

et al. 1999

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“…The populations of the various cluster types are then well known. 9,11 As discussed later, deviations from a random distribution can be detected by analyzing the measured magnetization curve at low temperatures. The ability to detect such deviations is a major advantage.…”

Section: Theorymentioning

confidence: 99%

“…More recently the six types of quartets in the fcc lattice were considered also. 9 Assuming that J is negative (antiferromagnetic), the magnetization curve at low T (k B T << |J|) for clusters of a given type has two main features: a quick saturation of the zero-field moment followed by a series of MST's. 8,9 This behavior is illustrated by the exact calculation of the magnetization curve for small clusters in this simple model.…”

Section: Theorymentioning

confidence: 99%

“…For five of the six types of quartets the series of MSTs end at 28|J|; only the "string quartet" ramp ends at a lower field gµ B H = 24.2|J|. 9 The exchange constant J is usually obtained from the observed H n for pairs since, except for singles, these are the most numerous. As was done in Ref.…”

Section: Theorymentioning

confidence: 99%

“…In the present work the simulations were improved by adding the contributions of the six types of quartets. 9 In addition a rough estimate of the contribution of clusters larger than quartets was also included, as will be discussed shortly, so that all the spins were accounted for.…”

Section: Theorymentioning

confidence: 99%

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Eu-Eu exchange interaction and Eu distribution inPb1−xEuxTefrom magnetizatio

et al. 1997

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The magnetization of Pb1−xEuxTe samples with x = 1.9, 2.6 and 6.0% was measured at 20 mK in fields up to 50 kOe, and at 0.6 K in fields up to 180 kOe. The 20 mK data show the magnetization steps (MSTs) arising from pairs and from triplets. The pair MSTs are used to obtain the dominant Eu-Eu antiferromagnetic exchange constant, J/kB = −0.264 ± 0.018 K. The exchange constant for triplets is the same. Comparison of the magnetization curves with theoretical simulations indicates that the Eu ions are not randomly distributed over all the cation sites. The deviation from a random distribution is much smaller if J is assumed to be the nearest-neighbor exchange constant J1 rather than the next-nearest-neighbor exchange constant J2. On this basis, J is tentatively identified as J1. However, the possibility that J = J2 cannot be excluded completely. To obtain agreement with the data, it must be assumed that the Eu ions tend to bunch together. Comparision with microprobe data indicates that the length scale for these concentration variations is smaller than a few µm. The theoretical simulations in the present work improve on those performed earlier by including clusters larger than three spins.75.50. Pp, 75.30.Et, 75.60.Ej

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Information theoretic approach provides a reliable description for kinetic component of correlation energy density functional

Badooei

2018

Int J of Quantum Chemistry

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In recent years, much efforts have been invested to apply information theory for different physical and chemical problems. In this regard, one can make use of one or many of the information theoretic quantities together within an approach so‐called information functional theory to describe the energetic components and electronic properties of various systems. In the present contribution, several information theoretic quantities such as Fisher information, Shannon entropy, Onicescu information energy, and Ghosh–Berkowitz–Parr entropy based on the two representations of electron density and shape function are utilized for the prediction of kinetic component of the correlation energy density functional as an important quantity in density functional theory. Taking the atoms and isoelectronic series as benchmark sets we find that with more or less different accountabilities of the considered quantities they can be introduced as reliable measures for the kinetic energy functional. Concerning different natures of the information theoretic quantities with variety of scaling properties and physiochemical propensities, it is shown that instead of describing all data using one of such quantities individually, considering all of them concurrently provides a better view on the prediction of the kinetic component of correlation energy density functional. Hopefully, the information theoretic approach can provide an alternative pathway toward the theoretical prediction and rationalization of important quantities in density functional calculations from the perspective of information theory.

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Magnetization steps of spin quartets

Cited by 19 publications

References 16 publications

Magnetization steps in[Fe(salen)Cl]2

Magnetization steps in[Fe(salen)Cl]2

Eu-Eu exchange interaction and Eu distribution inPb1−xEuxTefrom magnetizatio

Information theoretic approach provides a reliable description for kinetic component of correlation energy density functional

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