Effect of anisotropy on small magnetic clusters

Hucht, Alfred; Sahoo, Sanjubala; Sil, Shreekantha; Entel, P.

doi:10.1103/physrevb.84.104438

Cited by 23 publications

(17 citation statements)

References 46 publications

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“…It must also be noted that the on-site repulsion has been found to be stronger for C 20 than C 60 in numerical calculations [21,22], providing further support for the validity of the AHM as a very good approximation of the Hubbard model for the dodecahedron. Work closely related to the above has also been published in the literature [23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Ground state magnetic response of two coupled dodecahedra

Konstantinidis¹

2015

J. Phys.: Condens. Matter

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The antiferromagnetic Heisenberg model on the dodecahedron possesses a number of ground state magnetization discontinuities in a field at the classical and quantum level, even though it lacks magnetic anisotropy. Here the model is considered for two dodecahedra coupled antiferromagnetically along one of their faces, as a first step to determine the magnetic response of collections of fullerene molecules. The magnetic response is determined from the competition among the intra-, interdodecahedral exchange and magnetic field energies. At the classical level the discontinuities of the isolated dodecahedron are renormalized by the interdodecahedral coupling, while new ones show up, with the maximum number of ground state discontinuities being six for a specific range of the coupling. In the full quantum limit where the individual spin magnitude s = 1 2 , there are two ground state discontinuities originating in the single discontinuity of the isolated dodecahedron, and another one due to the intermolecular coupling, generating a total of three discontinuities which come one right after the other. These results show that the magnetic response of more than one dodecahedra interacting together is quite richer than the one of a single dodecahedron.

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Section: Introductionmentioning

confidence: 99%

Ground state magnetic response of two coupled dodecahedra

Konstantinidis¹

2015

J. Phys.: Condens. Matter

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“…Recently, it has been theoretically verified that quantum Heisenberg spin clusters can also exhibit the marked Schottky maxima due to a mutual competition between antiferromagnetic interactions and magnetic field [16][17][18][19]. The essential ingredient for observing the Schottky anomaly in the specific heat of antiferromagnetic Heisenberg spin clusters are abrupt magnetization jumps, which appear in a stepwise magnetization curve including one or more intermediate plateaus due to a crossing of energy levels [20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

The Schottky-type specific heat as an indicator of relative degeneracy between ground and first-excited states: The case study of regular Ising polyhedra

Karľová

Strečka

Madaras

2016

Physica B: Condensed Matter

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The specific heat of regular Ising polyhedra is investigated in detail as a function of temperature and magnetic field. It is shown that the regular Ising polyhedra display diverse double-peak temperature dependences of the specific heat whenever the magnetic field approaches a level-crossing field. The Schottky theory of a two-level system often provides a plausible explanation of a height and position of low-temperature peak, which emerges in the specific heat of a regular Ising polyhedron due to low-lying excitations from a ground state to a first-excited state. The height and position of Schottky-type maximum depends essentially on a relative degeneracy of the ground state and first-excited state, which are in general quite distinct in geometrically frustrated Ising spin clusters. Low-temperature variations of the specific heat with the magnetic field exhibit multipeak structure with two peaks (of generally different height) symmetrically placed around each level-crossing field.

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“…The above results demonstrate strong correlations between spatial symmetry and magnetic response for fullerene molecules. Such correlations have also been found between the dodecahedron and the icosahedron [10], both of them being Platonic solids [35], with the latter the smallest cluster with I h symmetry which is however not a fullerene and is made up only of triangles [36][37][38][39][40][41][42][43][44][45][46]. It is noted here that the inclusion of higher-order exchange terms significantly enhances the discontinuous magnetic response [47,48].…”

Section: Introductionmentioning

confidence: 58%

Zero-temperature magnetic response of small fullerene molecules at the classical and full quantum limit

Konstantinidis

2018

Journal of Magnetism and Magnetic Materials

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The ground-state magnetic response of fullerene molecules with up to 36 vertices is calculated, when spins classical or with magnitude s = 1 2 are located on their vertices and interact according to the nearest-neighbor antiferromagnetic Heisenberg model. The frustrated topology, which originates in the pentagons of the fullerenes and is enhanced by their close proximity, leads to a significant number of classical magnetization and susceptibility discontinuities, something not expected for a model lacking magnetic anisotropy. This establishes the classical discontinuities as a generic feature of fullerene molecules irrespective of their symmetry. The largest number of discontinuities have the molecule with 26 sites, four of the magnetization and two of the susceptibility, and an isomer with 34 sites, which has three each. In addition, for several of the fullerenes the classical zero-field lowest energy configuration has finite magnetization, which is unexpected for antiferromagnetic interactions between an even number of spins and with each spin having the same number of nearest-neighbors. The molecules come in different symmetries and topologies and there are only a few patterns of magnetic behavior that can be detected from such a small sample of relatively small fullerenes. Contrary to the classical case, in the full quantum limit s = 1 2 there are no discontinuities for a subset of the molecules that was considered. This leaves the icosahedral symmetry fullerenes as the only ones known supporting ground-state magnetization discontinuities for s = 1 2 . It is also found that a molecule with 34 sites has a doubly-degenerate ground state when s = 1 2 .

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Effect of anisotropy on small magnetic clusters

Cited by 23 publications

References 46 publications

Ground state magnetic response of two coupled dodecahedra

Ground state magnetic response of two coupled dodecahedra

The Schottky-type specific heat as an indicator of relative degeneracy between ground and first-excited states: The case study of regular Ising polyhedra

Zero-temperature magnetic response of small fullerene molecules at the classical and full quantum limit

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