Polarized neutron scattering in magnets

Maleev, S. V.

doi:10.1070/pu2002v045n06abeh001017

Cited by 90 publications

(63 citation statements)

References 123 publications

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“…In this case the imaginary part of the chirality is ω-even and the chiral contribution to the static susceptibility is equal to zero in agreement with the general theory 23 . Experimentally this contribution could be measured using circularly polarized AC field.…”

Section: Epr and Neutron Scatteringsupporting

confidence: 68%

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Cubic magnets with Dzyaloshinskii-Moriya interaction at low temperature

2006

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Ground state and spin-wave spectrum of cubic magnets with the Dzyaloshinskii-Moriya interaction (DMI) such as M nSi and F eGe are studied theoretically. Following interactions are taken into account: conventional isotropic exchange, the DMI, anisotropic exchange, magnetic dipole interaction and Zeeman energy. In the classical approximation these interactions determine the helix wave -vector k and critical field Hc for the transition to the "ferromagnetic" spin configuration. This field depends on the sample form due to the demagnetization. The linear spin-wave theory is developed. The spin-wave spectrum depends strongly on the magnetic field. At H > Hc we have quadratic spectrum with the gap linearly increasing with the field. Below Hc the spectrum is gapless and strongly anisotropic. It is a result of incommensurate magnetic structure when the DMI breaks the total spin conservation law and umklapp processes appear connecting the spin-wave excitations with momenta q and q ± k with different energies. For q along k the spectrum is linear. For other q directions it have very complex form determined by solution of infinite set of linear equations connecting the states with q and q ± nk where n = 1, 2, .... Restriction to n = 1 gives six equations which general solution remains complex. For q ⊥ k there are two modes: one has the gap equal to Ak 2 √ 2 where A is the spin-wave stiffness at q ≫ k. The second is gapless and proportional to q 2 ⊥ . At q ⊥ ≫ k all branches merge and the anisotropy of the spectrum disappears. These results changes insignificantly in n = 2 approximation.The classical energy depends on the field component along the helix axis k only. However it is known experimentally that rather weak perpendicular field rotates the helix and its axis is settled along the field. This quantum phenomenon is a consequence of the umklapps too. The spin-wave spectrum is unstable at infinitesimal perpendicular field. If the gap ∆ is introduced the spectrum becomes stable if gµBH ⊥ < ∆ In this field there are the magnetization along H ⊥ and deformation of the helix. The gap appears due to cubic anisotropy and the spin-wave interaction considered in the Hartree-Fock approximation.Peculiar properties of the ESR and neutron scattering in the helical magnets are considered and possibilities of corresponding experimental studies are discussed.

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Section: Epr and Neutron Scatteringsupporting

confidence: 68%

“…Functions Imχ ⊥ and ImC determine parts of the neutron scattering cross section independent on the neutron polarization P 0 and proportion to it respectively (See for example 23 ). The chiral contribution to the cross section appears due to the DM interaction and is q odd in agreement with general theory 23 .…”

Section: Epr and Neutron Scatteringmentioning

confidence: 99%

Cubic magnets with Dzyaloshinskii-Moriya interaction at low temperature

2006

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“…Maleyev [9][10][11], en utilisant la théorie standard des perturbations, a trouvé que les termes INM sont reliés aux fonctions de corrélation à trois spins, selon l'expression :…”

Section: Polarimétrie Sphérique Sur Cugeounclassified

“…Pour un système ne présentant pas d'ordre à longue distance, comme c'est le cas de CuGeO 3 , les termes scalaires d'échange de Heisenberg ne contribuent pas aux INM et seul le terme de Dzyloshinski-Moriya peut donner un effet. D'après la théorie générale [10,11,64], l'expression donnant les termes INM contient des facteurs de la forme 1…”

Section: Polarimétrie Sphérique Sur Cugeounclassified

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Polarimétrie neutronique longitudinale et sphérique en diffusion inélastique

Regnault

2007

Journées de la Neutronique

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Résumé. Dans ce cours, nous allons présenter les principes généraux de l'analyse de polarisation neutronique longitudinale et sphérique, en mettant un accent plus particulier sur le cas de la diffusion inélastique des neutrons. La force de la polarimétrie neutronique en diffusion inélastique sera illustrée sur des exemples caractéristiques choisis dans les domaines du magnétisme de terres-rares anormales, du magnétisme de systèmes de spins classiques et quantiques à basse dimension et de la supraconductivitéĹ haute température critique. NOTATIONSEnergie des neutrons incidents (également notée E i )

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Short-Range Order Above TC

Melnikov

Reser

2018

Dynamic Spin-Fluctuation Theory of Metallic Magnetism

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Polarized neutron scattering in magnets

Cited by 90 publications

References 123 publications

Cubic magnets with Dzyaloshinskii-Moriya interaction at low temperature

Cubic magnets with Dzyaloshinskii-Moriya interaction at low temperature

Polarimétrie neutronique longitudinale et sphérique en diffusion inélastique

Short-Range Order Above TC

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