TY - JOUR

T1 - Calculation of the Cross Sections for Neutron Scattering at Spin Waves in Helimagnets

AU - Pshenichnyi, K. A.

AU - Altynbaev, E. V.

AU - Grigoriev, S. V.

N1 - Publisher Copyright: © 2018, Pleiades Publishing, Ltd.

PY - 2018/5/1

Y1 - 2018/5/1

N2 - An analytical dependence of the cross section for the small-angle scattering of polarized neutrons at spin waves in helimagnets formed because of Dzyaloshinskii—Moriya interaction in cubic crystals without an inversion center (the space group is P213) is obtained. It is assumed that the dispersion of spin waves in helimagnets with the wave vector ks polarized by a magnetic field is larger than the critical field HC2 of the transition to the ferromagnetic phase and has the form Eq = A(q − ks ) + gμB(H − HС2). It is shown that the cross section for neutron scattering at the two-dimensional map of angles (θx, θy) is two circles of the radii θC with the centers ±θS, corresponding to the Bragg angle of diffraction by a helix oriented along the applied magnetic field H. The radii of these two circles θC are directly related to the stiffness of spin waves A of the magnetic system and depends on the applied magnetic field: θC2=θ02−gμBHEnθ0, where θ0=h22Amn and En and mn are the neutron energy and mass. It is shown that the scattering cross section depends on the neutron polarization, which is evidence of the chiral character of spin waves in the Dzyaloshinskii—Moriya helimagnets even in the completely polarized phase. The cases of neutron scattering at magnons where θ0 ≤ θS and θS ≥ θ0 are considered. The case of neutron scattering at spin waves in helimagnets is compared with analogous scattering at ferromagnets where θS → 0.

AB - An analytical dependence of the cross section for the small-angle scattering of polarized neutrons at spin waves in helimagnets formed because of Dzyaloshinskii—Moriya interaction in cubic crystals without an inversion center (the space group is P213) is obtained. It is assumed that the dispersion of spin waves in helimagnets with the wave vector ks polarized by a magnetic field is larger than the critical field HC2 of the transition to the ferromagnetic phase and has the form Eq = A(q − ks ) + gμB(H − HС2). It is shown that the cross section for neutron scattering at the two-dimensional map of angles (θx, θy) is two circles of the radii θC with the centers ±θS, corresponding to the Bragg angle of diffraction by a helix oriented along the applied magnetic field H. The radii of these two circles θC are directly related to the stiffness of spin waves A of the magnetic system and depends on the applied magnetic field: θC2=θ02−gμBHEnθ0, where θ0=h22Amn and En and mn are the neutron energy and mass. It is shown that the scattering cross section depends on the neutron polarization, which is evidence of the chiral character of spin waves in the Dzyaloshinskii—Moriya helimagnets even in the completely polarized phase. The cases of neutron scattering at magnons where θ0 ≤ θS and θS ≥ θ0 are considered. The case of neutron scattering at spin waves in helimagnets is compared with analogous scattering at ferromagnets where θS → 0.

KW - chirality

KW - cubic crystals without an inversion center

KW - helimagnet

KW - polarized neutrons

KW - scattering cross section

KW - spin waves

UR - http://www.scopus.com/inward/record.url?scp=85048701862&partnerID=8YFLogxK

U2 - 10.1134/S1027451018030163

DO - 10.1134/S1027451018030163

M3 - Article

AN - SCOPUS:85048701862

VL - 12

SP - 408

EP - 418

JO - ПОВЕРХНОСТЬ. РЕНТГЕНОВСКИЕ, СИНХРОТРОННЫЕ И НЕЙТРОННЫЕ ИССЛЕДОВАНИЯ

JF - ПОВЕРХНОСТЬ. РЕНТГЕНОВСКИЕ, СИНХРОТРОННЫЕ И НЕЙТРОННЫЕ ИССЛЕДОВАНИЯ

SN - 1027-4510

IS - 3

ER -