Deciphering the origin of giant magnetic anisotropy and fast quantum tunnelling in Rhenium(IV) single-molecule magnets

Singh, Saurabh Kumar; Rajaraman, Gopalan

doi:10.1038/ncomms10669

Cited by 38 publications

(35 citation statements)

References 73 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This opens the gateway to studying the pressure-dependent magnetic behaviour of the relatively large number of anisotropic, monomeric transition metal complexes which also order at low temperatures. One can imagine similarly impressive results in such systems, particularly for 5d metal ions on account of their increased magnetic anisotropy arising from their substantial spin–orbit coupling constants and the larger diffuseness of their magnetic orbitals when compared with those of the 3d and 4d ions44. Indeed the linear increase in T c with pressure seen here suggests that enhancement rates in other species may be much larger and that pressure could be employed to invoke transition from paramagnetism to LRMO.…”

Section: Discussionmentioning

confidence: 66%

Pressure induced enhancement of the magnetic ordering temperature in rhenium(IV) monomers

et al. 2016

View full text Add to dashboard Cite

Materials that demonstrate long-range magnetic order are synonymous with information storage and the electronics industry, with the phenomenon commonly associated with metals, metal alloys or metal oxides and sulfides. A lesser known family of magnetically ordered complexes are the monometallic compounds of highly anisotropic d-block transition metals; the ‘transformation' from isolated zero-dimensional molecule to ordered, spin-canted, three-dimensional lattice being the result of through-space interactions arising from the combination of large magnetic anisotropy and spin-delocalization from metal to ligand which induces important intermolecular contacts. Here we report the effect of pressure on two such mononuclear rhenium(IV) compounds that exhibit long-range magnetic order under ambient conditions via a spin canting mechanism, with Tc controlled by the strength of the intermolecular interactions. As these are determined by intermolecular distance, ‘squeezing' the molecules closer together generates remarkable enhancements in ordering temperatures, with a linear dependence of Tc with pressure.

show abstract

Section: Discussionmentioning

confidence: 66%

Pressure induced enhancement of the magnetic ordering temperature in rhenium(IV) monomers

et al. 2016

View full text Add to dashboard Cite

show abstract

“…This has led to increased interest in the giant magnetic anisotropy offered by certain 4f/5f ions with unquenched orbital angular momenta, and selected 4d/5d metal ions possessing considerable spin-orbit coupling. 5,[7][8][9][10][11] The 5d 3 Re IV ion is characterised by large magnetic anisotropy originating from second order spin-orbit coupling, with λ ≈ 1000 cm −1 for the free ion, often resulting in large values of the axial zero field splitting parameter, D. 12,13 In addition, the diffuse nature of the 5d orbitals gives rise to significant spin delocalisation onto the ligand atoms directly bonded to it, leading to non-negligible intermolecular magnetic exchange interactions, commonly mediated by Re-X⋯ X-Re [14][15][16][17][18][19] or Re-X⋯H 2 O⋯X-Re contacts. 20 Extensive research on the hexahalorhenate moiety [Re IV X 6 ] 2− (X = F, Cl, Br or I) has shown that the magnetic behaviour of the anion in the solid state depends greatly on the nature of the cation employed.…”

Section: Introductionmentioning

confidence: 99%

Hexahalorhenate(iv) salts of metal oxazolidine nitroxides

et al. 2017

View full text Add to dashboard Cite

Eight coordination compounds of formulae [Fe(L˙)][ReCl] (1a), [Fe(L˙)][ReBr] (1b), [Co(L˙)][ReCl]·CHCN (2a), [Co(L˙)][ReBr] (2b), [Ni(L˙)(CHCN)][ReCl]·CHCN (3a), [Ni(L˙)(CHCN)][ReBr]·3CHCN (3b), [Cu(L˙)][ReCl] (4a) and [Cu(L˙)][ReBr] (4b), where L˙ is the aminoxyl radical chelating ligand, 4,4'-dimethyl-2,2'-di(2-pyridyl)oxazolidine-N-oxide, have been synthesised. Structural and magnetic studies reveal metal-radical intramolecular antiferromagnetic interactions in the [M(L˙)] cations in the iron, cobalt and copper based compounds (1a, 1b, 2a, 2b, 4a and 4b) with the central metal ion low-spin in the case of iron (1a and 1b) and a gradual, cobalt based, spin-crossover transition present in 2a and 2b. The nickel based compounds, 3a and 3b, were analysed in the dried form (3a(dried) and 3b(dried)) and directly in acetonitrile (3a(solvated) and 3b(solvated)). Microanalysis and IR spectroscopy on 3a(dried) and 3b(dried) suggest that the dried samples are best formulated as [Ni(L˙)(HO)][ReX], where X = Cl (3a(dried)) and Br (3b(dried)). All forms of 3a and 3b exhibit cationic metal-radical ferromagnetic interactions resulting in S = 3/2 ground states. In addition, 3a(dried) exhibits spin-canting behaviour with an ordering temperature of 2.7 K, an open hysteresis loop with a coercive field H = 580 Oe, and a remanent magnetisation M = 0.21μ, resulting in a canting angle of ∼1.8°. In contrast, 3b(dried) shows no spin-canting behaviour; a maximum in χvs. T at T = 3 K suggesting long-range antiferromagnetic ordering. 3a(solvated) and 3b(solvated) show no indication of long-range magnetic ordering, unlike 4a and 4b where anomalies are evident in the low-temperature magnetic susceptibility measurements.

show abstract

“…These cause the relaxation to occur with lower energy barrier leading to smaller blocking temperature ( T B ), and is often much smaller than effective energy barrier, U eff , in SIMs. Among other factors that influence the QTM in transition‐metal SIMs, transverse components of anisotropy ( E ) play an important role in controlling QTM . Whereas, Orbach relaxation can be facilitated through higher excited states if one has strong axial ligand‐field environment around metal ions in the absence or presence of very weak transverse ligand field.…”

Section: Introductionmentioning

confidence: 99%

A Design Criteria to Achieve Giant Ising‐Type Anisotropy in Co^II‐Encapsulated Metallofullerenes

Singh

Shukla

Khatua

et al. 2019

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

Discovery of permanent magnetisation in molecules just like in hard magnets decades ago led to the proposal of utilising these molecules for information storage devices and also as Q‐bits in quantum computing. A significant breakthrough with a blocking temperature as high as 80 K has been recently reported for lanthanocene complexes. While enhancing the blocking temperature further remains one of the primary challenges, obtaining molecules that are suitable for the fabrication of the devices sets the bar very high in this area. Encouraged by the fact that our earlier predictions of potential single‐molecule magnets (SMMs) in lanthanide‐containing endohedral fullerenes have been verified, here we set out to undertake a comprehensive study on CoII‐ion‐encapsulated fullerene as potential SMMs. To study this class of molecules, we have utilised an array of theoretical methods ranging from density functional to ab initio CASSCF/NEVPT2 methods for obtaining reliable estimate of zero‐field splitting parameters D and E. Additionally, we have also employed, for the first time a combination of molecular dynamics based on DFT methods coupled with CASSCF/NEVPT2 methods to seek the role of conformational isomers in the relaxation of magnetisation. Particularly, we have studied, Co@C28, Co@C38 and Co@C48 cages and their isomers as potential target molecules that could yield substantial magnetic anisotropy. Our calculations categorically reveal a very large Ising anisotropy in this class of molecules, with Co@C48 cages predicted to yield D values as high as −127 cm−1. Our calculations on the smaller cages reveal the free movement of CoII ion inside the cage, leading to the likely scenario of faster relaxation of magnetisation. However, larger fullerene cages were found to solve this issue. Further models with incorporating units such as {CoOZn}, {CoScZnN} inside larger fullerenes yield axial zero‐field splitting values as high as −200 cm−1 with negligible E/D values. As these units represent a strong axiality coupled with a viable way to obtain air‐stable low‐coordinate CoII complexes, this opens up a new paradigm in the search of SMMs in this class of molecules.

show abstract

Deciphering the origin of giant magnetic anisotropy and fast quantum tunnelling in Rhenium(IV) single-molecule magnets

Cited by 38 publications

References 73 publications

Pressure induced enhancement of the magnetic ordering temperature in rhenium(IV) monomers

Pressure induced enhancement of the magnetic ordering temperature in rhenium(IV) monomers

Hexahalorhenate(iv) salts of metal oxazolidine nitroxides

A Design Criteria to Achieve Giant Ising‐Type Anisotropy in Co^II‐Encapsulated Metallofullerenes

Contact Info

Product

Resources

About

Deciphering the origin of giant magnetic anisotropy and fast quantum tunnelling in Rhenium(IV) single-molecule magnets

Cited by 38 publications

References 73 publications

Pressure induced enhancement of the magnetic ordering temperature in rhenium(IV) monomers

Pressure induced enhancement of the magnetic ordering temperature in rhenium(IV) monomers

Hexahalorhenate(iv) salts of metal oxazolidine nitroxides

A Design Criteria to Achieve Giant Ising‐Type Anisotropy in CoII‐Encapsulated Metallofullerenes

Contact Info

Product

Resources

About

A Design Criteria to Achieve Giant Ising‐Type Anisotropy in Co^II‐Encapsulated Metallofullerenes