Can large magnetic anisotropy and high spin really coexist?

Ruiz, Eliseo; Cirera, Jordi; Cano, Joan; Álvarez, Santiago; Loose, Claudia; Kortus, Jens

doi:10.1039/b714715e

Cited by 231 publications

(160 citation statements)

References 24 publications

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“…one anticipates only a moderate increase in the barrier (a factor of ~1.45 -1.75) upon switching from low-to high-spin, and a factor of less than two upon doubling the nuclearity (spin). The concept of D decreasing as S increases is not new [16][17][18][19][20][26][27][28]. However, our results paint a slightly more optimistic view in comparison to two previous works suggesting that U does not increase upon increasing S [26,27].…”

Section: The Connection Between D Mol and D Ioncontrasting

confidence: 56%

Magnetic quantum tunneling: insights from simple molecule-based magnets

et al. 2010

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This perspectives article takes a broad view of the current understanding of magnetic bistability and magnetic quantum tunneling in single-molecule magnets (SMMs), focusing on three families of relatively simple, low-nuclearity transition metal clusters: spin S = 4 II 4 Ni , III 3 Mn (S = 2 and 6) and III 6 Mn (S = 4 and 12). The Mn III complexes are related by the fact that they contain triangular III 3 Mn units in which the exchange may be switched from antiferromagnetic to ferromagnetic without significantly altering the coordination around the Mn III centers, thereby leaving the single-ion physics more-or-less unaltered. This allows for a detailed and systematic study of the way in which the individual-ion anisotropies project onto the molecular spin ground state in otherwise identical low-and high-spin molecules, thus providing unique insights into the key factors that control the quantum dynamics of SMMs, namely: (i) the height of the kinetic barrier to magnetization relaxation; and (ii) the transverse interactions that cause tunneling through this barrier. Numerical calculations are supported by an unprecedented experimental data set (17 different compounds), including very detailed spectroscopic information obtained from high-frequency electron paramagnetic resonance and low-temperature hysteresis measurements. Comparisons are made between the giant spin and multi-spin phenomenologies. The giant spin approach assumes the ground state spin, S, to be exact, enabling implementation of simple anisotropy projection techniques. This methodology provides a basic understanding of the concept of anisotropy dilution whereby the cluster anisotropy decreases as the total spin increases, resulting in a barrier that depends weakly on S. This partly explains why the record barrier for a SMM (86 K for Mn 6 ) has barely increased in the 15 years since the first studies of Mn 12 -acetate, and why the tiny Mn 3 molecule can have a barrier approaching 60% of this record. Ultimately, the giant spin approach fails to capture all of the key physics, although it works remarkably well for the purely ferromagnetic cases. Nevertheless, diagonalization of the multi-spin Hamiltonian matrix is necessary in order to fully capture the interplay between exchange and local anisotropy, and the resultant spin-state mixing which ultimately gives rise to the tunneling matrix elements in the high symmetry SMMs (ferromagnetic Mn 3 and Ni 4 ). The simplicity (low-nuclearity, high-symmetry, weak disorder, etc..) of the molecules highlighted in this study proves to be of crucial importance. Not only that, these simple molecules may be considered among the best SMMs: Mn 6 possesses the record anisotropy barrier, and Mn 3 is the first SMM to exhibit quantum tunneling selection rules that reflect the intrinsic symmetry of the molecule.

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Section: The Connection Between D Mol and D Ioncontrasting

confidence: 56%

Magnetic quantum tunneling: insights from simple molecule-based magnets

et al. 2010

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“…The current approach to obtain SIMs with high anisotropy barriers and high blocking temperatures involves replacing large clusters of 3d metals with lanthanide complexes [8,9]. The unquenched angular momentum of the lanthanides ensures intrinsic magnetic anisotropy and large magnetic moments, and a thermal energy barrier up to 915 K has been reported for a terbium(III) bis-phthalocyaninato complex [10].…”

Section: Introductionmentioning

confidence: 99%

Field-induced single-ion magnetic behaviour in a highly luminescent Er3+ complex

Coutinho

Pereira

Martín-Ramos

et al. 2015

Materials Chemistry and Physics

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“…It is well known that these SMMs have a large highspin ground state (S) in combination with a large easy-axis type magnetic anisotropy (D), presenting slow relaxation of the magnetization of purely molecular origin [9]. It has been nearly twenty years since the first discovery that the Mn 12 cluster with a bistable ground state shows slow magnetic relaxation. Initially, most efforts were dedicated to obtaining high-spin, strongly-coupled transition-metal SMMs such as the Mn 12 derivatives [9,10] and Fe 8 iron complexes [11].…”

mentioning

confidence: 99%

“…Initially, most efforts were dedicated to obtaining high-spin, strongly-coupled transition-metal SMMs such as the Mn 12 derivatives [9,10] and Fe 8 iron complexes [11]. However, theoretical study based on experiments suggests that large magnetic anisotropy is not helped by a high spin state of the ground state for transition-metal systems, which has been a crucial roadblock to obtaining systems with larger energy barriers [12,13]. Nevertheless, since Ishikawa et al [14] discovered lanthanide double-decker complexes [Pc 2 Ln] − TBA + (Ln = Tb III , Dy III , Ho III ; TBA + = N(C 4 H 9 ) + ) functioning as very efficient SMMs, the complexes containing lanthanide elements are highlighted and large numbers of Lanthanide-based Single Molecule Magnets (Ln-SMMs) with larger energy barriers have evolved, especially Dy-based complexes with various nuclearities from Dy 1 [15], Dy 2 [16,17], Dy 3 [18,19], Dy 4 [20,21], Dy 6 [22], Dy 10 [23] to Dy 26 [24].…”

mentioning

confidence: 99%

Modulating the magnetic relaxation of lanthanide-based single-molecule magnets

Zhang

Xue

et al. 2012

Chin. Sci. Bull.

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In the area of molecular magnetism, single molecule magnets (SMMs) containing lanthanide elements are of immense scientific and technological interest because of their large energy barriers and high measured hysteresis temperature. Although there has been significant progress in the synthesis and characterization of lanthanide-based SMMs, there are still challenges, for instance, how single-ion anisotropy of lanthanide elements can be exploited, and how zero-field tunneling of magnetization can be suppressed. This article is devoted to the progress in various methodologies for modulating magnetic relaxation, especially in terms of crystal field and magnetic interactions. The crystal field plays a dominant role in creating single-molecule magnets with largely anisotropic f-elements, while the strong coupling between magnetic centers is able to suppress quantum tunneling of magnetization efficiently. lanthanide, single-molecule magnets, relaxation dynamics, quantum tunneling, magnetic coupling Citation:Zhang P, Zhang L, Xue S F, et al. [24]. These systems may hold the key to obtaining high anisotropic barrier single-molecule magnets (SMMs).Because of the effective shielding of the 4f electrons by the outer 5s 2 and 5p 6 shells of the Xe core, lanthanide ions are characterized by large unquenched orbital angular momentum, with the spin-orbit coupled ground state of 2S+1 L J

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Can large magnetic anisotropy and high spin really coexist?

Abstract: This theoretical study discusses the interplay of the magnetic anisotropy and magnetic exchange interaction of two Mn6 complexes and suggests that large magnetic anisotropy is not favoured by a high spin state of the ground state.

Cited by 231 publications

References 24 publications

Magnetic quantum tunneling: insights from simple molecule-based magnets

Magnetic quantum tunneling: insights from simple molecule-based magnets

Field-induced single-ion magnetic behaviour in a highly luminescent Er3+ complex

Modulating the magnetic relaxation of lanthanide-based single-molecule magnets

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