Crystallographic symmetry and magnetic structure of CoO

Jauch, W.; Reehuis, M.; Bleif, H.-J.; Kubanek, F.; Pattison, Philip

doi:10.1103/physrevb.64.052102

Cited by 212 publications

(244 citation statements)

References 12 publications

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“…Due to the limited neutron beam time we could measure enough data close to the antiferromagnetic phasetransition temperature and therefore the critical exponent ␤ and the Néel temperature T N could not be determined accurately from the present experiment. However the data are consistent with the reported 27 Néel temperature T N Ϸ 290 K. The identification of the order parameter with the energy of the inelastic signal works well in a single magnetic sublattice system such as CoO. It has been shown more rigorously in our recent paper 16 on NdAl 2 that the identification of the order parameter with the energy of the inelastic signal or the hyperfine splitting of the nuclear levels is justified.…”

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confidence: 80%

“…CoO along with other transition-metal oxides MnO, FeO, and NiO crystallize with the face-centered-cubic NaCl-type structure in the Fm3m space group. CoO orders [20][21][22][23][24][25][26][27] below T N Ϸ 290 K with the type-II structure with the propagation vector k = ͑ We performed inelastic neutron-scattering experiments on a CoO single crystal by using the high-resolution backscattering-neutron spectrometer SPHERES of the Jülich Centre for Neutron Science located at the FRMII reactor in Munich. The wavelength of the incident neutrons was = 6.271 Å.…”

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confidence: 99%

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Low-energy nuclear spin excitations in CoO

Chatterji

Schneider

2009

Phys. Rev. B

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We investigated the low-energy excitations in CoO in the eV range by a back-scattering-neutron spectrometer. The energy scans on a CoO single crystal revealed inelastic peaks at E = 2.05Ϯ 0.02 eV at T = 3.5 K on both energy-gain and energy-loss sides. The inelastic peaks move gradually toward lower energy with increasing temperature and finally merge with the elastic peak at the electronic magnetic ordering temperature T N Ϸ 290 K. We interpret the inelastic peaks to be due to the transition between hyperfine-split nuclear level of the The statics and dynamics of ordered nuclei in magnetic crystals have attracted some attention from the condensedmatter physicists. The experiments however are difficult due to the very low temperatures needed and also the due to the required energy resolution of the order of a eV or better of the neutron spectrometers to be used for such studies. Blume and Schermer 1 were the first to show the potential application of the neutron-scattering technique to study nuclear spin systems and calculated the relevant differential neutronscattering cross sections and final-state polarization for elastic-scattering processes. Later Word et al.2 extended these calculations to inelastic-scattering processes. investigated the hyperfine fields in Co-and V-based compounds by using high-resolution backscattering-neutron spectrometer. The hyperfine splitting lies typically in the energy range of a few eV. The inelastic spin-flip scattering of neutrons from the nuclear spins can yield this information provided the neutron spectrometer has the required resolution of about 1 eV or less and also the incoherent scattering of the nucleus is strong enough. It was established that the hyperfine field produced at the nucleus is roughly but not exactly proportional to the electronic magnetic moment of the 3d shell. Chatterji et al. [10][11][12][13][14][15][16] and also Przenioslo et al.17 investigated low-energy nuclear excitation in Nd and Nd-based compounds. Recently Ehlers et al. 18 reported observation of nuclear spin excitations in pyrochlore structure spin ice compound Ho 2 Ti 2 O 7 .The method of determining the hyperfine splitting of the nuclear levels by spin-flip scattering of neutrons is now well established.3 The relevant neutron-scattering process can be summarized as follows: If neutrons with spin s are scattered from nuclei with spins I, the probability that their spins will be flipped is 2/3. The nucleus at which the neutron is scattered with a spin flip, changes its magnetic quantum number M to M Ϯ 1 due to the conservation of the angular momentum. If the nuclear ground state is split up into different energy levels E M due to the hyperfine magnetic field or an electric quadrupole interaction, then the neutron spin flip produces a change in the ground-state energy ⌬E = E M − E MϮ1 . This energy change is transferred to the scattered neutron. If there is only one isotope then one expects a central elastic peak and two inelastic peaks of approximately equal intensities. The element Co is such ...

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confidence: 80%

mentioning

confidence: 99%

Low-energy nuclear spin excitations in CoO

Chatterji

Schneider

2009

Phys. Rev. B

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“…Here, the crystal structure is that of a cubic rock salt. It has been well-documented [33,34] how the establishment of AF2 magnetic order prompts a distortion of the crystalline lattices in these materials below T N . By including relativistic effects, such as spin-orbit coupling, into our description of the TMOs in principal it should be possible to deduce how these magnetostrictive effects arise at T N as the symmetry is broken.…”

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confidence: 99%

Onset of magnetic order in strongly-correlated systems fromab initioelectronic structure calculations: application to transition metal oxides

et al. 2008

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We describe an ab initio theory of finite temperature magnetism in strongly-correlated electron systems. The formalism is based on spin density functional theory, with a self-interaction corrected local spin density approximation (SIC-LSDA). The self-interaction correction is implemented locally, within the KKR multiplescattering method. Thermally induced magnetic fluctuations are treated using a meanfield 'disordered local moment' (DLM) approach and at no stage is there a fitting to an effective Heisenberg model. We apply the theory to the 3d transition metal oxides, where our calculations reproduce the experimental ordering tendencies, as well as the qualitative trend in ordering temperatures. We find a large insulating gap in the paramagnetic state which hardly changes with the onset of magnetic order.

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confidence: 99%

“…At any wave-vector transfer, Q, up to as many as four spin wave modes may arise from domain structure for any particular spin or orbit transition due to the domain structure. The nearest neighbour exchange is frustrated, contributing no molecular field, and it is the next nearest neighbour exchange that breaks the symmetry below T N = 290 K. The nature of the order and fluctuations is still controversial [4,5].We have made high-resolution measurements of the magnetic excitations in the (HHL) plane of a highquality crystal of CoO at 6 K, 320 K and 450 K. In the first set of experiments, with a focusing PG(002) monochromator and flat PG analyzer with E f =3.52 THz, a resolution of 1.2 THz was achieved at 10 THz energy transfer. In a second set of measurements, with a Be(002) monochromator and PG(002) analyzer set to E f =7.37 THz, a resolution of 0.8 THz was achieved for excitations at 10 THz.…”

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confidence: 99%

Orbital and spin excitations in cobalt oxide

Yamani¹,

Buyers

Cowley

et al. 2008

Physica B: Condensed Matter

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By means of neutron scattering we have determined new branches of magnetic excitations in orbitally active CoO (T N =290 K) up to 15 THz and for temperatures from 6 K to 450 K. Data were taken in the (111) direction in six single-crystal zones. From the dependence on temperature and Q we have identified several branches of magnetic excitation. We describe a model for the coupled orbital and spin states of Co 2+ subject to a crystal field and tetragonal distortion. Cobaltous oxide is a face-centred antiferromagnet in which (111) ferromagnetic sheets of spins stack antiferromagnetically along [111] directions. At any wave-vector transfer, Q, up to as many as four spin wave modes may arise from domain structure for any particular spin or orbit transition due to the domain structure. The nearest neighbour exchange is frustrated, contributing no molecular field, and it is the next nearest neighbour exchange that breaks the symmetry below T N = 290 K. The nature of the order and fluctuations is still controversial [4,5].We have made high-resolution measurements of the magnetic excitations in the (HHL) plane of a highquality crystal of CoO at 6 K, 320 K and 450 K. In the first set of experiments, with a focusing PG(002) monochromator and flat PG analyzer with E f =3.52 THz, a resolution of 1.2 THz was achieved at 10 THz energy transfer. In a second set of measurements, with a Be(002) monochromator and PG(002) analyzer set to E f =7.37 THz, a resolution of 0.8 THz was achieved for excitations at 10 THz.With both configurations we resolved four peaks at 6 K in the excitation spectrum between 4 and 12 THz as shown in Fig. 1 for different magnetic zones. In a recent study only two broad modes in the same spectral range were detected [6]. Analysis including the Co 2+ magnetic form factor shows that the peak at 9.5 THz is magnetic in origin. The intensities of the peaks at 6.5 THz and 7.6 THz decrease with Q by less than the form factor, suggesting these peaks are

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Crystallographic symmetry and magnetic structure of CoO

Cited by 212 publications

References 12 publications

Low-energy nuclear spin excitations in CoO

Low-energy nuclear spin excitations in CoO

Onset of magnetic order in strongly-correlated systems fromab initioelectronic structure calculations: application to transition metal oxides

Orbital and spin excitations in cobalt oxide

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