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- Title
Investigation of the chiral structure of the Y/Dy multilayer system by the method of the small-angle scattering of polarized neutrons.
- Authors
Grigor'ev, S. V.; Okorokov, A. I.; Chetverikov, Yu. O.; Chernyshev, D. Yu.; Eckerlebe, H.; Pranzas, K.; Schreyer, A.
- Abstract
The magnetic spiral structure of a Y/Dy sample has been investigated for temperatures from 30 to 190 K by the method of the small-angle scattering of polarized neutrons. The sample is a sequence of layers Y50 nm [Dy4.3 nm /Y2.8 nm ]350/Y234 nm /Nd200 nm Al2O3 (substrate) that is grown as a single crystal with the [001] axis of the hexagonal lattice, which is perpendicular to the layer plane. The experiments demonstrate the appearance of the magnetic peak below T N = 165.4 K, which is associated with the helicoidal phase, and the helicoid coherence length is larger than the layer thickness of the Y/Dy layer. The use of polarized neutrons allows the separation of the polarization-independent and polarization-independent components of magnetic scattering. The polarization-independent component of the magnetic neutron cross section is proportional to magnetization squared 〈 S Z 〉2, whereas the polarization-dependent component is proportional to the average chirality of the system 〈 C〉 = 〈[· S 1 × S 2]〉. The critical exponents βC = 1.02(1) and β = 0.39(1) have been determined for the average chirality and magnetization, respectively. The magnetization critical exponent β for Dy/Y coincides with the exponent obtained for Dy bulk samples. The difference βC − 2β = 0.24(2) shows that the chirality can be a component of the order parameter that is independent of magnetization. This experiment corroborates the results that were obtained for the critical chirality in Ho and were reported in Phys. Rev. B 64, 100402(R) (2001).
- Subjects
NEUTRON polarization; LATTICE dynamics; TEMPERATURE effect; ANGULAR distribution (Nuclear physics); MAGNETIZATION; COHERENCE (Physics); CHIRALITY
- Publication
JETP Letters, 2006, Vol 83, Issue 11, p478
- ISSN
0021-3640
- Publication type
Article
- DOI
10.1134/S0021364006110026