Synthesis, Crystal Structure, and Magnetic Properties of Quasi-One-Dimensional Oxides Ca3CuMnO6 and Ca3Co1+xMn1−xO6

Зубков, В. Г.; Базуев, Г. В.; Tyutyunnik, A. P.; Berger, I. F.

doi:10.1006/jssc.2001.9198

Cited by 82 publications

(81 citation statements)

References 15 publications

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“…In contrast, the effective magnetic moment of µ eff =5.8-6.0 µ B per formula unit (f.u. ), extracted from magnetic susceptibility measurements above T N [4,5], suggests that both Co 2+ and Mn 4+ are in a HS state. Thus there is an apparent controversy between those data, and the problem concerning the spin state of, in particular, Co 2+ ions seems to be still unsolved.…”

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“…The spin chain has the alternate trigonal prismatic and octahedral sites [3,4]. Special ↑↑↓↓ antiferromagnetic (AF) structure is detected in Ca 3 CoMnO 6 below T N ≈13 K by neutron diffraction.…”

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confidence: 99%

“…Among a variety of multiferroic materials discovered so far [1,2], ferroelectric Ising chain magnet Ca 3 CoMnO 6 is quite unique, because the ferroelectricity (FE) is driven by exchange striction in a collinear Ising spin chain consisting of the charge ordered transition-metal ions [3]. The spin chain has the alternate trigonal prismatic and octahedral sites [3,4]. Special ↑↑↓↓ antiferromagnetic (AF) structure is detected in Ca 3 CoMnO 6 below T N ≈13 K by neutron diffraction.…”

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confidence: 99%

“…We took the experimental centrosymmetric structure data of the rhombohedral lattice (R-3c) which has in a hexagonal setting the lattice constant a=9.1314Å and c=10.5817Å [4,7]. The calculations were done for different magnetic structures (↑↓↑↓, ↑↑↓↓, ↑↓↓↓, and ↑↑↑↑ orderings in the Co-Mn-CoMn chains).…”

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Ising Magnetism and Ferroelectricity inCa3CoMnO6

Burnus

et al. 2009

Phys. Rev. Lett.

131

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The origin of both the Ising chain magnetism and ferroelectricity in Ca3CoMnO6 is studied by ab initio electronic structure calculations and x-ray absorption spectroscopy. We find that Ca3CoMnO6 has the alternate trigonal prismatic Co 2+ and octahedral Mn 4+ sites in the spin chain. Both the Co 2+ and Mn 4+ are in the high spin state. In addition, the Co 2+ has a huge orbital moment of 1.7 µB which is responsible for the significant Ising magnetism. The centrosymmetric crystal structure known so far is calculated to be unstable with respect to exchange striction in the experimentally observed ↑↑↓↓ antiferromagnetic structure for the Ising chain. The calculated inequivalence of the Co-Mn distances accounts for the ferroelectricity.PACS numbers: 78.70.Dm, 71.27.+a Among a variety of multiferroic materials discovered so far [1,2], ferroelectric Ising chain magnet Ca 3 CoMnO 6 is quite unique, because the ferroelectricity (FE) is driven by exchange striction in a collinear Ising spin chain consisting of the charge ordered transition-metal ions [3]. The spin chain has the alternate trigonal prismatic and octahedral sites [3,4]. Special ↑↑↓↓ antiferromagnetic (AF) structure is detected in Ca 3 CoMnO 6 below T N ≈13 K by neutron diffraction. However, the measured magnetic moment of 0.66 µ B /Co and 1.93 µ B /Mn is much smaller than the expected one of the normal high-spin (HS) Co 2+ (S=3/2) and Mn 4+ (S=3/2). This led Choi et al. to a conclusion that the Co 2+ is (surprisingly) in a low-spin (LS) state [3]. In contrast, the effective magnetic moment of µ eff =5.8-6.0 µ B per formula unit (f.u.), extracted from magnetic susceptibility measurements above T N [4,5], suggests that both Co 2+ and Mn 4+ are in a HS state. Thus there is an apparent controversy between those data, and the problem concerning the spin state of, in particular, Co 2+ ions seems to be still unsolved. Another important question is to understand the nature of the Ising magnetism and of the resulting exchange striction, which are apparently crucial for the appearance of FE in Ca 3 CoMnO 6 . To this end, we carried out ab initio electronic structure calculations and x-ray absorption spectroscopy (XAS). We address the important issues including the Co/Mn site preference, their charge/spin/orbital states, the origin of the Ising magnetism, and the exchange striction.Our ab initio calculations were performed by using the full-potential augmented plane waves plus local orbital method (Wien2k code) [6]. We took the experimental centrosymmetric structure data of the rhombohedral lattice (R-3c) which has in a hexagonal setting the lattice constant a=9.1314Å and c=10.5817Å [4,7]. The calculations were done for different magnetic structures (↑↓↑↓, ↑↑↓↓, ↑↓↓↓, and ↑↑↑↑ orderings in the Co-Mn-CoMn chains). To study the exchange striction effect, we investigated the effect of internal atomic relaxation allowing the inversion symmetry to be broken in the ↑↑↓↓ spin chain, as discussed below. The muffin-tin sphere radii are chosen to be 2.4, 2.1 and 1.4 Bohr for ...

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Ising Magnetism and Ferroelectricity inCa3CoMnO6

Burnus

et al. 2009

Phys. Rev. Lett.

131

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“…The polarization of 2870 mC m À2 observed in CaMn 7 O 12 is unprecedented for improper ferroelectric multiferroics driven by magnetic helicity and is the combined effect of the inverse Dzyaloshinskii-Moriya mechanism and symmetric exchange striction. 101 103,104 The Co 2 þ trigonal crystal field and spin-orbit coupling results in a large Co 2 þ magnetic moment of 1.7 m B and strong Ising behavior that keeps the magnetic moment rigidly along the spin chain direction. 105 Figure 5(c) shows that parallel neigbouring spins that tend to shorten the bond length, whereas an antiparallel spin alignement leads to bond extension.…”

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Multiferroic Materials: Physics and Properties

Palstra

Blake

2016

Reference Module in Materials Science and Materials Engineering

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Multiferroics are materials in which magnetism and ferroelectricity coexist. They are of fundamental interest to understand electronic behavior coupling magnetic interactions and electric dipolar order. Moreover, they are of applied interest because they allow various types of novel magnetic and electric device structures. We distinguish two important classes of multiferroic materials and discuss mechanisms and materials belonging to each class separately. In the first group of multiferroics, magnetization and polarization arise independently from each other. In the second category of multiferroics, ferroelectricity is induced by magnetic order, resulting in strong magnetoelectric coupling. We also briefly discuss multiferroic thin film heterostructures showing interfacial magnetoelectric coupling interactions with potential applications in memory devices

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Magnetic Properties from the Perspectives of Electronic Hamiltonian

Whangbo

Xiang

2017

Handbook of Solid State Chemistry

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In this chapter, we review the quantitative and qualitative aspects of describing the properties of magnetic solids on the basis of electronic Hamiltonian that describes the energy states of a magnetic system using both orbital and spin degrees of freedom. To quantitatively discuss a magnetic property of a given magnetic system, one needs to generate the spectrum of its energy states and subsequently average the properties of these states with each state weighted by its Boltzmann distribution factor. Currently, this is an impossible task to achieve on the basis of an electronic Hamiltonian, so it is necessary to resort to a simple model Hamiltonian, that is, a spin Hamiltonian that describes the energy states of a magnetic system using only the spin degree of freedom. We show that a spin Hamiltonian approach becomes consistent with an electronic Hamiltonian approach if the spin lattice and its associated spin exchange parameters, to be used for the spin Hamiltonian, are determined by the energy‐mapping analysis based onDFTcalculations. The preferred spin orientation (i.e., the magnetic anisotropy) of a magnetic ion is not predicted by a spin Hamiltonian because it does not include the orbital degree of freedom explicitly. In contrast, the magnetic anisotropy is readily predicted by electronic structure theories employing both orbital and spin degrees of freedom, if one takes into consideration the spin–orbit coupling (SOC), , of a magnetic ion where and are, respectively, the spin and orbital operators and λ theSOCconstant. It was shown that the preferred spin orientation of a magnetic ion can be predicted and understood in terms of theHOMO–LUMOinteractions of the magnetic ion by takingSOC, , as perturbation. A spin Hamiltonian gives rise to the spin‐half misconception, namely, the blind belief that spin‐half magnetic ions do not possess magnetic anisotropy that arise fromSOC. This misconception contradicts not only experimental observations on spin‐half ions but also theoretical results based onDFTcalculations and perturbation theory analyses based on an electronic Hamiltonian. This misconception is a direct consequence from the limitedness of a spin Hamiltonian that it lacks the orbital degree of freedom. We show that the magnetic properties of 5dion oxides are better explained by theLS‐coupling than by thejj‐coupling scheme ofSOC, and the spin‐orbital entanglement of 5dions is not as strong as has been assumed.

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Synthesis, Crystal Structure, and Magnetic Properties of Quasi-One-Dimensional Oxides Ca3CuMnO6 and Ca3Co1+xMn1−xO6

Cited by 82 publications

References 15 publications

Ising Magnetism and Ferroelectricity inCa3CoMnO6

Ising Magnetism and Ferroelectricity inCa3CoMnO6

Multiferroic Materials: Physics and Properties

Magnetic Properties from the Perspectives of Electronic Hamiltonian

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