Measurement of Spin-Wave Dispersion in NiO by Inelastic Neutron Scattering and Its Relation to Magnetic Properties

Hutchings, M. T.; Samuelsen, Emil J.

doi:10.1103/physrevb.6.3447

Cited by 381 publications

(313 citation statements)

References 55 publications

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“…The antiferromagnetic order in NiO ͑111͒ consists of spins oriented along the three ͗112͘ directions, which lie in the ͑111͒ plane. 30 The ferromagnetic ͑111͒ sheets stack antiferromagnetically in the ͗111͘ direction. Due to the lack of in-plane anisotropy, all possible spin orientations exist within the plane.…”

Section: Ni Cantingmentioning

confidence: 99%

Origin of the interlayer exchange coupling in[Co∕Pt]∕NiO∕[Co∕
Baruth
¹
,
Keavney
²
,
Burton
³

et al. 2006
Phys. Rev. B

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The origin of the oscillatory interlayer exchange coupling in ͓Co/ Pt͔ / NiO / ͓Co/ Pt͔ multilayers is investigated using advanced microscopy and spectroscopy techniques and micromagnetic modeling. X-ray magnetic circular dichroism ͑XMCD͒ measurements show the presence of the canting of Ni spins in the NiO film being greater for antiferromagnetically coupled multilayers than for ferromagnetically coupled ones. This behavior is consistent with the model, which assumes a different sign of the exchange coupling at the two interfaces and the antiferromagnetic layer-by-layer coupling in the NiO film. An unexpectedly short attenuation length of 4 Å for secondary electrons in NiO is measured, which has implications for the interpretation of XMCD data. Domain images obtained using XMCD-photoemission electron microscopy at the Co and Ni resonances indicate that the canting of the Ni spins occurs on both a microscopic and macroscopic scale. The average size of the domains is shown to increase with exchange coupling strength. In antiferromagnetically coupled samples, the competition between magnetostatic and interlayer exchange effects gives rise to a region of overlapping domains. The size of this region scales inversely with coupling strength. Finally, the temperature dependence of the interlayer coupling shows both reversible and irreversible effects. The irreversible effects stem from oxidation/reduction reactions at the Co/ NiO interface. The reversible effects stem from the temperature dependences of the many factors that play a role in the interlayer coupling and exhibit nonmonotonic temperature dependence.

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Section: Ni Cantingmentioning

confidence: 99%

Origin of the interlayer exchange coupling in[Co∕Pt]∕NiO∕[Co∕
Baruth
¹
,
Keavney
²
,
Burton
³

et al. 2006
Phys. Rev. B

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“…Magnetic exchange interactions in NiO have been calculated [7][8][9] and have also been determined by measuring the spin-wave dispersion by inelastic neutron scattering. 10 The spin-wave dispersion in NiO could be described by a nearest-neighbor ͑NN͒ ferromagnetic exchange interaction J 1 = 1.37 meV and a next-nearest-neighbor ͑NNN͒ antiferromagnetic exchange interaction J 2 = −19.01 meV. In addition an anisotropy of the form 12 as J 2 = ͑10Dq / 3͒ 2 / U eff , where 10Dq is the crystal-field splitting and U eff is the Coulomb interaction.…”

mentioning

confidence: 99%

“…The first-principles calculation 9 of J 1 is also very close to the experimental value. 10 So in NiO the NNN superexchange interaction J 2 is much stronger than the direct NN interaction J 1 . J 2 determines the magnetic ordering and related properties whereas the weak J 1 has been proved to play a decisive role in the weak structural distortion.…”

mentioning

confidence: 99%

“…Magnetic exchange interactions in NiO have been calculated 7-9 and have also been determined by measuring the spin-wave dispersion by inelastic neutron scattering. 10 The spin-wave dispersion in NiO could be described by a nearest-neighbor ͑NN͒ ferromagnetic exchange interaction J 1 = 1.37 meV and a next-nearest-neighbor ͑NNN͒ antiferromagnetic exchange interaction J 2 = −19.01 meV. In addition an anisotropy of the form D 1 S x 2 + D 2 S y 2 where x is perpendicular to the plane, and y within, is needed to describe the data, with D 1 = 1.13 K and D 2 = 0.06 K. These parameters give a mean-field Néel temperature 10 of T N ͑MF͒ = 886 K. The calculated exchange interaction values are very close to these experimental values.…”

mentioning

confidence: 99%

“…Using these values J 2 is calculated to be J 2 = 19.44 meV which is surprisingly close to the J 2 = 19.01 meV determined from inelastic neutron scattering. 10 The weak ferromagnetic NN interaction is presumably due to the combined effects of superexchange and direct exchange. The first-principles calculation 9 of J 1 is also very close to the experimental value.…”

mentioning

confidence: 99%

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Antiferromagnetic phase transition and spin correlations in NiO

2009

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We have investigated the antiferromagnetic ͑AF͒ phase transition and spin correlations in NiO by hightemperature neutron diffraction below and above T N . We show that AF phase transition is a continuous second-order transition within our experimental resolution. The spin correlations manifested by the strong diffuse magnetic scattering persist well above T N Ϸ 530 K and could still be observed at T = 800 K which is about 1.5T N . We argue that the strong spin correlations above T N are due to the topological frustration of the spins on a fcc lattice. The Néel temperature is substantially reduced by this process. We determined the critical exponents ␤ = 0.328Ϯ 0.002 and = 0.64Ϯ 0.03 and the Néel temperature T N = 530Ϯ 1 K. These critical exponents suggest that NiO should be regarded as a 3dXY system. DOI: 10.1103/PhysRevB.79.172403 PACS number͑s͒: 75.25.ϩz Transition-metal oxides have been the subject of renewed interest ever since high-temperature superconductivity was discovered in cuprate materials. The transition-metal oxides with narrow d bands form strongly correlated electron systems or a Mott-Hubbard system in which Coulomb interactions between electrons lead to a breakdown of the conventional band theory. In such a system, hole or electron doping may transform an insulating antiferromagnet into a highly correlated metal. 1,2 In selected copper oxides, the metal can superconduct, while in others it is a strongly renormalized Fermi liquid. In manganites for example the doping transforms the insulating antiferromagnet into a ferromagnetic metal with colossal magnetoresistive properties. 3 Among the transition-metal oxides the antiferromagnetic NiO plays a key role in the studies of the electronic and magnetic properties of correlated 3d-electron system. NiO, along with other transition-metal oxides MnO, FeO, and CoO, crystallizes with the face-centered-cubic ͑space group Fm3m͒ NaCl-type structure. The magnetic properties of pure NiO are well known. Ni 2+ ions in NiO are in an S = 1 state and order at T N = 530 K in the type-II antiferromagnetic structure with the propagation vector k = ͑ 1 2 , 1 2 , 1 2 ͒. Ferromagnetic ͑111͒ layers are antiferromagnetically stacked along the ͓111͔ direction. The magnetic moments of Ni lie in the ͑111͒ plane and there is now considerable evidence that they lie in the ͓1,1,−2͔ direction. 4 There is a rhombohedral distortion at T N which increases as the temperature is lowered. The electronic structure of NiO has been extensively investigated. [5][6][7] There are strong indications that NiO is a charge-transfer insulator 5 in which the top of the valence band is primarily formed by oxygen 2p states, while the bottom of the conduction band is Ni-3d like. The insulating state is characterized by a band gap of about 4 eV. Magnetic exchange interactions in NiO have been calculated 7-9 and have also been determined by measuring the spin-wave dispersion by inelastic neutron scattering. 10 The spin-wave dispersion in NiO could be described by a nearest-neighbor ͑NN͒ ferromag...

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Spin Structures and Spin Wave Excitations

Zaliznyak

2007

Handbook of Magnetism and Advanced Magnetic Materials

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Electronic spin interactions and the resulting spin structures which give rise to various kinds of magnetism existing in many‐electron condensed matter systems are discussed. In most cases, spin structure and excitations in a spin system can be understood in the framework of semiclassical spin‐wave theory. Basic examples observed in magnetic neutron diffraction and inelastic magnetic neutron scattering experiments are presented and discussed with reference to such description. Relationship between the structure of the crystal lattice and spin arrangement and energy dispersion of spin excitations in the crystal are discussed and illustrated by some recent experimental results.

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Measurement of Spin-Wave Dispersion in NiO by Inelastic Neutron Scattering and Its Relation to Magnetic Properties

Cited by 381 publications

References 55 publications

Origin of the interlayer exchange coupling in[Co∕Pt]∕NiO∕[Co∕
Baruth
¹
,
Keavney
²
,
Burton
³

et al. 2006
Phys. Rev. B

Origin of the interlayer exchange coupling in[Co∕Pt]∕NiO∕[Co∕
Baruth
¹
,
Keavney
²
,
Burton
³

et al. 2006
Phys. Rev. B

Antiferromagnetic phase transition and spin correlations in NiO

Spin Structures and Spin Wave Excitations

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Measurement of Spin-Wave Dispersion in NiO by Inelastic Neutron Scattering and Its Relation to Magnetic Properties

Cited by 381 publications

References 55 publications

Origin of the interlayer exchange coupling in[Co∕Pt]∕NiO∕[Co∕Baruth1, Keavney2, Burton3 et al. 2006Phys. Rev. B

Origin of the interlayer exchange coupling in[Co∕Pt]∕NiO∕[Co∕Baruth1, Keavney2, Burton3 et al. 2006Phys. Rev. B

Antiferromagnetic phase transition and spin correlations in NiO

Spin Structures and Spin Wave Excitations

Contact Info

Product

Resources

About

Origin of the interlayer exchange coupling in[Co∕Pt]∕NiO∕[Co∕
Baruth
¹
,
Keavney
²
,
Burton
³

et al. 2006
Phys. Rev. B

Origin of the interlayer exchange coupling in[Co∕Pt]∕NiO∕[Co∕
Baruth
¹
,
Keavney
²
,
Burton
³

et al. 2006
Phys. Rev. B