Zero-field slow magnetic relaxation from single Co(ii) ion: a transition metal single-molecule magnet with high anisotropy barrier

Zhu, Yuan‐Yuan; Cui, Chuanyong; Zhang, Yi‐Quan; Jia, Jun-Hua; Guo, Xiao; Chen, Gao; Kang, Qian; Jiang, Shang‐Da; Wang, Bing‐Wu; Wang, Zheming; Gao, Song

doi:10.1039/c3sc21893g

Cited by 301 publications

(103 citation statements)

References 57 publications

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“…The double well model holds up in the case of monometallic cobalt(II) SMMs with negative D values [9,[11][12][13][14][15][16][17][18][19], but the observation of similar behaviour in monometallic cobalt(II) complexes with positive D values [20][21][22] suggests that the picture is more complex. Indeed, slow relaxation in positive-D compounds is a phenomenon that is not yet fully understood-although attempts have been made to explain it [23,24].…”

Section: Introductionmentioning

confidence: 90%

Evidence of Slow Magnetic Relaxation in Co(AcO)2(py)2(H2O)2

et al. 2016

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Abstract:The monometallic pseudo-octahedral complex, [Co(H 2 O) 2 (CH 3 COO) 2 (C 5 H 5 N) 2 ], is shown to exhibit slow magnetic relaxation under an applied field of 1500 Oe. The compound is examined by a combination of experimental and computational techniques in order to elucidate the nature of its electronic structure and slow magnetic relaxation. We demonstrate that any sensible model of the electronic structure must include a proper treatment of the first-order orbital angular momentum, and we find that the slow magnetic relaxation can be well described by a two-phonon Raman process dominating at high temperature, with a temperature independent quantum tunnelling pathway being most efficient at low temperature.

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Section: Introductionmentioning

confidence: 90%

Evidence of Slow Magnetic Relaxation in Co(AcO)2(py)2(H2O)2

et al. 2016

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“…This situation, together with the fact that mononuclear species can exhibit larger anisotropies than their multinuclear counterparts (the control of the total anisotropy in polymetallic systems is extremely difficult), has prompted the search for SMMs based on mononuclear Co II complexes with an S =3/2 ground state. Results in this field are limited to nine examples with pseudotetrahedral, square‐pyramidal, rhombic octahedral, or triangular prismatic geometries,8a–g two of which display easy‐plane anisotropy ( D >0). For Co II systems with D >0, the direct spin‐phonon relaxation process between the Ms =±1/2 ground Kramers doublet is forbidden in zero field.…”

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confidence: 99%

Slow Magnetic Relaxation in a Co^II–Y^III Single‐Ion Magnet with Positive Axial Zero‐Field Splitting

et al. 2013

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With the discovery of molecular complexes exhibiting slow relaxation of the magnetization and magnetic hysteresis at low temperature, research activity in the field of molecular magnetism based on coordination compounds has experienced spectacular growth. [1] These nanomagnets, called single-molecule magnets (SMMs), [1][2][3] straddle the quantum/ classical interface showing quantum effects, such as quantum tunneling of the magnetization and quantum phase interference, and have potential applications in molecular spintronics, ultra-high density magnetic information storage, and quantum computing at the molecular level. [3] The motivation of much of this research activity has been provided by the prospect of integrating SMMs into nanosized devices. The origin of the SMM behavior is the existence of an energy barrier that prevents reversal of the molecular magnetization, [1] although the currently observed energy barriers are (relatively) low and therefore SMMs act as magnets only at very low temperature. To increase the height of the energy barrier and therefore to improve the SMM properties, systems with large spin-ground states and/or with large magnetic anisotropy are required. The early examples of SMMs were clusters of transition metal ions, [2] but recently mixed 3d/4f metal aggregates, [4] low-nuclearity 4f metal complexes, [5] and even mononuclear complexes (called single-ion magnets, SIMs) of lanthanide, [6] actinide, [7] and transition-metal ions [8] have been reported to exhibit slow relaxation of the magnetization.It should be noted that for integer-spin systems with D < 0 fast quantum tunneling of the magnetization (QTM) through the mixing of AE Ms levels may suppress the observation of slow magnetic relaxation through a thermally activated mechanism. QTM is promoted by transverse zero-field splitting (E), hyperfine interactions, and/or dipolar interactions. [1] The application of a small direct current (dc) field, stabilizing the negative Ms levels with regard to the positive ones, may remove the degeneracy of the AE Ms levels on either side of the energy barrier, tilting the system out of resonance and, on occasion, enabling the thermally activated mechanism. For non-integer spin systems with D < 0, the mixing of the degenerate ground state AE Ms levels through transverse anisotropy (E) is forbidden, thus favoring observation of the thermally activated relaxation process. [9] This situation, together with the fact that mononuclear species can exhibit larger anisotropies than their multinuclear counterparts (the

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“…Due to single-ion anisotropy, several mononuclear Co(II) complexes exhibit slow magnetic relaxation under non-zero DC field [1]. With a high-spin cobalt(II), a complex with a Co(SCN) 2 fragment is known to have relatively large magnetic anisotropy which is used to prepare single molecular magnets [2].…”

Section: Discussionmentioning

confidence: 99%

Crystal structure of bis(isothiocyanato-κN)bis(4,4',5,5'-tetrahydro-2,2'-bithiazole-κ2N,N')cobalt(II), C14H16CoN6S6

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Liu

et al. 2013

Zeitschrift Für Kristallographie - New Crystal Structures

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Source of materialA solution of NH 4 SCN (9.8 mg, 0.12 mmol) in 3 ml methanol was slowly added to a mixture of Co(ClO 4 ) 2 ·6H 2 O (44.2 mg, 0.17 mmol) and 4,4',5,5'-tetrahydro-2,2'-bithiazole (bt) (17.2 mg, 0.1 mmol) in methanol (5 ml) with general stirring. The mixture was placed in the dark, and blue well-shaped crystals were obtained after one week, in a yield of 35% (based on Co). Experimental detailsOther H atoms were included in the refinement at calculated positions [C-H aromatic = 0.93 Å] and treated as riding models with U iso (H) = 1.2U eq (C). DiscussionDue to single-ion anisotropy, several mononuclear Co(II) complexes exhibit slow magnetic relaxation under non-zero DC field [1]. With a high-spin cobalt(II), a complex with a Co(SCN) 2 fragment is known to have relatively large magnetic anisotropy which is used to prepare single molecular magnets [2]. For this purpose, the title compound has been synthesized and the crystal structure determined. The molecular structure of the title structure is made up of discrete neutral [Co(bt) 2 (NCS) 2 ] complex. The cobalt atom lies at the center of a distorted octahedron [CoN 6 ] defined by two bt ligands arranged in a cis conformation. The two remaining coordination positions are occupied by two isothiocyanato ligands. The average Co-N bond lengths of the isocyanato ligands are shorter than those of the bt ligands, which was also observed for some Fe complexes [3]. In the crystal structure, there is a S···S intermolecular contact between the S1 atom of the isothiocyanato group and the S5 atom of the bt ring from an adjacent complex.

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Zero-field slow magnetic relaxation from single Co(ii) ion: a transition metal single-molecule magnet with high anisotropy barrier

Cited by 301 publications

References 57 publications

Evidence of Slow Magnetic Relaxation in Co(AcO)2(py)2(H2O)2

Evidence of Slow Magnetic Relaxation in Co(AcO)2(py)2(H2O)2

Slow Magnetic Relaxation in a Co^II–Y^III Single‐Ion Magnet with Positive Axial Zero‐Field Splitting

Crystal structure of bis(isothiocyanato-κN)bis(4,4',5,5'-tetrahydro-2,2'-bithiazole-κ2N,N')cobalt(II), C14H16CoN6S6

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Zero-field slow magnetic relaxation from single Co(ii) ion: a transition metal single-molecule magnet with high anisotropy barrier

Cited by 301 publications

References 57 publications

Evidence of Slow Magnetic Relaxation in Co(AcO)2(py)2(H2O)2

Evidence of Slow Magnetic Relaxation in Co(AcO)2(py)2(H2O)2

Slow Magnetic Relaxation in a CoII–YIII Single‐Ion Magnet with Positive Axial Zero‐Field Splitting

Crystal structure of bis(isothiocyanato-κN)bis(4,4',5,5'-tetrahydro-2,2'-bithiazole-κ2N,N')cobalt(II), C14H16CoN6S6

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Slow Magnetic Relaxation in a Co^II–Y^III Single‐Ion Magnet with Positive Axial Zero‐Field Splitting