Crystal Structure and Possible Charge Ordering in One-Dimensional Ca3Co2O6

Fjellvåg, Helmer; Gulbrandsen, Egil; Aasland, S.; Olsen, A.; Hauback, Bjørn C.

doi:10.1006/jssc.1996.0224

Cited by 291 publications

(220 citation statements)

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“…While the Co-Co distance within the chains amounts to 2.595Å, next-nearest neighbour distances across the chains are 5.31Å [2]. This value is somewhat larger than the interchain separation of 5.24Å, since neighbouring chains are shifted parallel to the trigonal axis by 1/3 of the intrachain separation.…”

Section: Introductionmentioning

confidence: 88%

Extended moment formation and magnetic ordering in the trigonal chain compound Ca3Co2O6

Eyert

Laschinger

Kopp

et al. 2004

Chemical Physics Letters

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The results of electronic structure calculations for the one-dimensional magnetic chain compound Ca 3 Co 2 O 6 are presented. The calculations are based on density functional theory and the local density approximation and used the augmented spherical wave (ASW) method. Our results allow for deeper understanding of recent experimental findings. In particular, alternation of Co 3d low-and high-spin states along the characteristic chains is related to differences in the oxygen coordination at the inequivalent cobalt sites. Strong hybridization of the d states with the O 2p states lays ground for polarization of the latter and the formation of extended localized magnetic moments centered at the high-spin sites. In contrast, strong metal-metal overlap along the chains gives rise to intrachain ferromagnetic exchange coupling of the extended moments via the d 3z 2 −r 2 orbitals of the low-spin cobalt atoms.

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Section: Introductionmentioning

confidence: 88%

Extended moment formation and magnetic ordering in the trigonal chain compound Ca3Co2O6

Eyert

Laschinger

Kopp

et al. 2004

Chemical Physics Letters

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“…Among spin-chain systems, the compound, Ca 3 Co 2 O 6 [Ref 1,2], crystallizing in a K 4 CdCl 6 -derived rhombohedral structure, has attracted a lot of attention theoretically as well as experimentally in recent years [see, for instance, references 3-13, and articles cited therein]. This is primarily associated with the intrinsic frustration of the magnetic coupling arising from the triangular arrangement of antiferromagnetically coupled ferromagnetic chains.…”

Section: Introductionmentioning

confidence: 99%

Negative chemical pressure effects induced by Y substitution for Ca on the ‘exotic’ magnetic behavior of the spin-chain compound, Ca3Co2O6

Rayaprol

Sampathkumaran

2005

Pramana - J Phys

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The magnetic behavior of a solid solution, Ca 3-x Y x Co 2 O 6 , based on an 'exotic' spin-chain compound, Ca 3 Co 2 O 6 , crystallizing in K 4 CdCl 6 -derived rhombohedral structure is investigated. Among the compositions investigated (x= 0.0, 0.3, 0.5, 0.75 and 1.0), single phase formation persists up to x= 0.75, with the elongation of the c-axis. The present investigations reveal that the temperature at which the 'so-called' 'partially disordered antiferromagnetic structure' sets in (which occurs at 24 K for the parent compound, x= 0.0) undergoes gradual reduction with the substitution of Y for Ca, attaining the value of about 2.2 K for the nominal x = 1.0. The trend observed in this characteristic temperature is opposite to that reported under external pressure, thereby establishing that Y substitution exerts negative chemical pressure. Anomalous steps observed in the isothermal magnetization at very low temperatures (around 2 K) for x= 0.0, which have been proposed to arise from 'quantum tunneling effects' are found to vanish by a small substitution (x = 0.3) of Y for Ca. Systematics in ac and dc magnetic susceptibility behavior with Y substitution for Ca have also been probed. We believe that the present results involving the expansion of chain length without disrupting the magnetic chain may be useful to the overall understanding of the novel magnetism of the parent compound.

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“…The origin of this intriguing phenomenon is still an open question [7,8] and the magnetic properties of Ca 3 Co 2 O 6 have been intensely studied in the past decade using many techniques, including x-ray [9,10,11] and neutron [12,13,14] Ca 3 Co 2 O 6 is a rare example of a material where ferromagnetic (FM) 1D Ising spin chains are coupled through a much weaker antiferromagnetic (AF) exchange on a triangular lattice. The spin chains in Ca 3 Co 2 O 6 are made up of alternating face-sharing octahedral (CoI) and trigonal prismatic (CoII) CoO 6 polyhedra, running along the c axis and arranged in a triangular lattice in the ab plane [17]. The different Co environments leave the Co 3+ ions on the CoI sites in a low-spin (S=0) state, and those on the CoII sites in the high-spin (S=2) state [9,11,15].…”

mentioning

confidence: 99%

Nature of the Magnetic Order inCa3Co2O6

et al. 2008

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We present a detailed powder and single crystal neutron diffraction study of the spin chain compound Ca3Co2O6. Below 25 K, the system orders magnetically with a modulated partially disordered antiferromagnetic structure. We give a description of the magnetic interactions in the system which is consistent with this magnetic structure. Our study also reveals that the long-range magnetic order co-exists with a shorter range order with a correlation length scale of ∼ 180Å in the ab plane. Remarkably, on cooling, the volume of material exhibiting short range order increases at the expense of the long-range order.PACS numbers: 75.30. Gw, 75.25.+z, 75.30.Fv, 75.50.Ee The appearance of plateaux in the magnetization curves of low dimensional quantum spin systems (e.g. NH 4 CuCl 3 [1] and SrCu 2 (BO 3 ) 2 [2]) has generated considerable attention from both an experimental and a theoretical point of view. In this respect the spin chain system Ca 3 Co 2 O 6 is very interesting because at low temperatures several steps, equally spaced in magnetic field, appear in the magnetization [3,4,5], a behavior reminiscent of quantum tunneling of magnetization in molecular magnets [6]. The origin of this intriguing phenomenon is still an open question [7,8] and the magnetic properties of Ca 3 Co 2 O 6 have been intensely studied in the past decade using many techniques, including x-ray [9,10,11] and neutron [12,13,14] Ca 3 Co 2 O 6 is a rare example of a material where ferromagnetic (FM) 1D Ising spin chains are coupled through a much weaker antiferromagnetic (AF) exchange on a triangular lattice. The spin chains in Ca 3 Co 2 O 6 are made up of alternating face-sharing octahedral (CoI) and trigonal prismatic (CoII) CoO 6 polyhedra, running along the c axis and arranged in a triangular lattice in the ab plane [17]. The different Co environments leave the Co 3+ ions on the CoI sites in a low-spin (S=0) state, and those on the CoII sites in the high-spin (S=2) state [9,11,15]. Crystalline electric fields also lead to a very strong anisotropy with the moments preferentially aligned along the c axis [3,4]. The zero-field magnetic structure of Ca 3 Co 2 O 6 has yet to be described unambiguously. Most theoretical descriptions of the magnetic structure center around the two stable configurations for 1D Ising chains coupled antiferromagnetically on a 2D triangular lattice, the ferrimagnetic structure (M, M, −M ) and the partially disordered antiferromagnetic (PDA) structure (M, −M, 0) [18] (the labels in parenthesis indicate the relative magnetizations on the triangular lattice). The step-like magnetization has been described using the Ising model on a triangular lattice [7]. There are, however, experimental data which suggest a more complex magnetic structure for Ca 3 Co 2 O 6 . A pronounced drop in the intensity of the magnetic peaks on cooling below 18 K in zero field has been observed in powder [12,13] and single crystal diffraction studies [14]. Recent resonant x-ray scattering (RXS) studies [10] showed a small (∼ 0.01Å −1 ) incommensu...

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Crystal Structure and Possible Charge Ordering in One-Dimensional Ca3Co2O6

Cited by 291 publications

References 5 publications

Extended moment formation and magnetic ordering in the trigonal chain compound Ca3Co2O6

Extended moment formation and magnetic ordering in the trigonal chain compound Ca3Co2O6

Negative chemical pressure effects induced by Y substitution for Ca on the ‘exotic’ magnetic behavior of the spin-chain compound, Ca3Co2O6

Nature of the Magnetic Order inCa3Co2O6

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