A Single‐Ion Magnet Based on a Heterometallic CoIII2DyIII Complex

Goura, Joydeb; Brambleby, Jamie; Goddard, Paul; Chandrasekhar, Vadapalli

doi:10.1002/chem.201406021

Cited by 34 publications

(32 citation statements)

References 46 publications

(37 reference statements)

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“…Figure 13(a-d) shows example a.c. susceptibility data for the single molecule magnet Co 2 Er [63] and a diagram of the molecular structure (figure 13(e)). Strictly this compound falls under the class of single ion magnets since only the rare earth ion possesses unpaired electrons and therefore a magnetic moment [22,63]. The Cole-Cole plot for this compound (shown in figure 14) agreed well with the generalised Cole-Cole model with fits showing a low α of ∼ 0.2-0.3 for 3-2 K [63].…”

Section: Superparamagnets and Single Molecule Magnetsmentioning

confidence: 56%

“…This effect has been studied in various chiral magnets, including MnSi [97], GaV 4 S 8 [98], Fe 1−x Co x Si [99] and Cu 2 OSeO 3 [100,95], and can be used to rather efficiently map out the phase boundaries and thus determine the phase diagram. An example is given in figure 23 [95] which displays a.c. susceptibility data on contour plots using the same B-T phase diagram as figure 22. This figure illustrates that a lot of information is obtainable by measuring a.c. susceptibility carefully over a restricted range of B and T .…”

Section: Long Range Magnetic Ordermentioning

confidence: 84%

“…Setting α = 0 corresponds to no spread of relaxation times and the ideal Debye model is recovered. This modification (shown in figures 5(a) and (d)) is successful in describing slowly relaxing electric [13] and magnetic systems [1,2,22,23]. An alternative approach is known as the Cole-Davidson model (shown in figures 5(b) and (e)) [24] which instead places an exponent β in the denominator as follows:…”

Section: A Range Of Relaxation Timesmentioning

confidence: 99%

“…Since each molecule of a SMM is identical (and rather well magnetically isolated from its neighbour), the relaxation time of each molecule might be expected to be identical, so that the ideal Debye model should hold rather well. In practice, there can be a range of coexisting relaxation processes, and data are better fitted by a generalized Debye model (equation (28)) with α = 0 [1,22,63]. Nevertheless, as the condition ωτ ≈ 1 is crossed on cooling, α can be observed to adopt small values indicating small spreads of relaxation times and the presence of Debyelike process [63].…”

Section: Superparamagnets and Single Molecule Magnetsmentioning

confidence: 99%

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A.C. susceptibility as a probe of low-frequency magnetic dynamics

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Blundell

2018

J. Phys.: Condens. Matter

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The experimental technique of a.c. susceptibility can be used as a probe of magnetic dynamics in a wide variety of systems. Its use is restricted to the lowfrequency regime and thus is sensitive to relatively slow processes. Rather than measuring the dynamics of single spins, a.c. susceptibility can be used to probe the dynamics of collective objects, such as domain walls in ferromagnets or vortex matter in superconductors. In some frustrated systems, such as spin glasses, the complex interactions lead to substantial spectral weight of fluctuations in the low-frequency regime, and thus a.c. susceptibility can play a unique role. We review the theory underlying the technique and magnetic dynamics more generally and give applications of a.c. susceptibility to a wide variety of experimental situations.

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Section: Superparamagnets and Single Molecule Magnetsmentioning

confidence: 56%

Section: Long Range Magnetic Ordermentioning

confidence: 84%

Section: A Range Of Relaxation Timesmentioning

confidence: 99%

Section: Superparamagnets and Single Molecule Magnetsmentioning

confidence: 99%

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A.C. susceptibility as a probe of low-frequency magnetic dynamics

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Blundell

2018

J. Phys.: Condens. Matter

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“…From our lab, we have previously reported heterometallic Zn II/ Ln III and Co III /Ln III complexes, both of which were shown to display SMM behavior . The Co III /Ln III complexes, in particular, displayed slow relaxation of the magnetization in zero‐field below 15 K; energy barriers of up to 88 K were found for the reversal of magnetization …”

Section: Introductionmentioning

confidence: 99%

Heterometallic Zn₃Ln₃ Ensembles Containing (μ₆‐CO₃) Ligand and Triangular Disposition of Ln³⁺ ions: Analysis of Single‐Molecule Toroic (SMT) and Single‐Molecule Magnet (SMM) Behavior

Goura

Colacio

Herrera

et al. 2017

Chemistry A European J

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Two new heterometallic Zn Ln (Ln =Dy, Tb) complexes, with a double triangular topology of the metal ions, have been assembled from the polytopic Mannich base ligand 6,6'-{[2-(dimethylamino)ethylazanediyl]bis(methylene)}bis(2-methoxy-4-methylphenol) (H L) with the aid of an in situ generated carbonate ligand from atmospheric CO fixation. Theoretical calculations indicate axial ground states for the Ln ions in these complexes, with their local magnetic moments being almost coplanar and tangential to the Ln atoms that define the equilateral triangle. Therefore, they can be considered as single-molecule toroics (SMTs) with almost zero total magnetic moment. Micro-SQUID measurements on the Dy counterpart show hysteresis loops below 3 K that have an S-shape, with large coercive fields opening upon cooling. This behavior is typical of a single molecule magnet (SMM) with very slow zero-field relaxation. At around ±0.35 T, the loops have a broad step, which is due to a direct relaxation process and corresponds to an acceleration of the relaxation of the magnetization, also observed at this magnetic field from ac susceptibility measurements. Simulations suggest that the broad step corresponds to two level avoidance of crossing points where the spin chiral Kramers doublet meets excited states of the coupled manifold, whose position is defined by exchange and dipole interactions. The Tb counterpart does not exhibit SMM behavior, which is due to the fact that the degeneracy of the ground state of the exchange coupled system is lifted at zero field, thus favoring quantum tunneling of magnetization (QTM).

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Heterometallic 3d–4f Complexes as Single‐Molecule Magnets

Dey

Acharya

Chandrasekhar

2019

Chemistry An Asian Journal

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Heterometallic 3d-4fc omplexes are being investigated, for some time, as being useful in molecular magnetism, particularly as single-molecule magnets (SMMs). This interest is primarily because of the possibility of an increased ligand-mediated super-exchange phenomenon between the 3d and 4f metal ions. Such an interaction, apart from bestowing af avorable ground-state spin to the complex, also assists in reducing quantum tunneling of magnetization that is widely prevalenti nS MMs making them to lose magnetization. However,a ssembling both 3d as well as 4f ions using same ligand system is challenging and involves the design of multi-site coordination ligandsw ith specific coordination compartments for the 3d and the 4f metal ions while at the same time allowing these disparate metal ions to be linked to each other through ab ridging ligatinga tom. This review presents as ummary of the 3d-4f complexes primarily derived from the author's work while alluding to importante xamplesf rom the literature. We also provide an outlookf or the future design of such complexes.[a] Dr.A .Dey, Prof. V. Chandrasekhar 4434Minireview dro-imidazol-2-ylidenea nd DmpN 3 = 2,6-dimesitylphenyl azide] which exhibit slow magnetic relaxation with U eff values of 450 and 413 cm À1 respectively. [13][14][15] Similarly,t here have been reports on mononuclear lanthanide complexes [12a, 16] ever since the seminalp aper on the first lanthanide based SMM in 2003, (Bu 4 N)[Ln III (Pc) 2 ] [17] [Ln III = Tb III (7)a nd Dy III (8); Pc = phthalocyaninato].R ecently,t he complexes [(Cp ttt ) 2 Dy III ][B(C 6 F 5 ) 4 ] [18] (9) (Cp ttt [19] (10)h ave been reported with blockingt emperatures of 60 and 80 Kr espectively.C omplex 10 holds the record for the highest reported energy barrier U eff = 1541 cm À1 for the reversal of magnetization.One of the problemsa ssociated with SMMs is that the magnetization can be lost by av ariety of ways including quantum tunneling mechanism (QTM) which shortcuts the energy barriers of relaxation. [6b] This is an important impediment and progress in this field is dependent on minimizing or eliminating QTM. There are many strategies to do this including assembling mononuclear complexes possessing point-group symmetries such as C 1v , D 1h , S 8 (I 4 ), D 4d , D 5d and D 5h[12a] or by increasing the ferromagnetic coupling between the adjacent lanthanide centers,a ne xample of this being the dinuclearc omplex [K(18crown-6)]{[((Me 3 Si) 2 n) 2 (THF)Dy III ] 2 (m-h 2 :h 2 -N 2 )} (11)w here the radicall igand, N 2 3À , [20] facilitates af erromagnetic exchange between the two lanthanide centers. [21] Another strategy is to involve heterometallic transition metal/lanthanide complexes where as uper-exchange ferromagnetic interaction between the lanthanide and transition metal ion can mitigate QTM. [22] Accordingly,t he first 3d-4fb ased SMM, a[ Cu II 2 Tb III 2 ]( 12) complex, was reported by Osa and co-workers in 2004. [23] Murray and co-workers have successfully utilized this strategy for av ariety of complexes with {Cr II...

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A Single‐Ion Magnet Based on a Heterometallic Co^III₂Dy^III Complex

Abstract: We report a Co(III) 2 Dy(III) complex, which shows single-ion-magnet behaviour. AC susceptibility data of this compound reveals the presence of slow relaxation of the magnetization in zero-field below 15 K. The relaxation barrier is 88 K.

Cited by 34 publications

References 46 publications

A.C. susceptibility as a probe of low-frequency magnetic dynamics

A.C. susceptibility as a probe of low-frequency magnetic dynamics

Heterometallic Zn₃Ln₃ Ensembles Containing (μ₆‐CO₃) Ligand and Triangular Disposition of Ln³⁺ ions: Analysis of Single‐Molecule Toroic (SMT) and Single‐Molecule Magnet (SMM) Behavior

Heterometallic 3d–4f Complexes as Single‐Molecule Magnets

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A Single‐Ion Magnet Based on a Heterometallic CoIII2DyIII Complex

Abstract: We report a Co(III) 2 Dy(III) complex, which shows single-ion-magnet behaviour. AC susceptibility data of this compound reveals the presence of slow relaxation of the magnetization in zero-field below 15 K. The relaxation barrier is 88 K.

Cited by 34 publications

References 46 publications

A.C. susceptibility as a probe of low-frequency magnetic dynamics

A.C. susceptibility as a probe of low-frequency magnetic dynamics

Heterometallic Zn3Ln3 Ensembles Containing (μ6‐CO3) Ligand and Triangular Disposition of Ln3+ ions: Analysis of Single‐Molecule Toroic (SMT) and Single‐Molecule Magnet (SMM) Behavior

Heterometallic 3d–4f Complexes as Single‐Molecule Magnets

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A Single‐Ion Magnet Based on a Heterometallic Co^III₂Dy^III Complex

Heterometallic Zn₃Ln₃ Ensembles Containing (μ₆‐CO₃) Ligand and Triangular Disposition of Ln³⁺ ions: Analysis of Single‐Molecule Toroic (SMT) and Single‐Molecule Magnet (SMM) Behavior