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Magnetic Diffraction Difference to nuclear scattering: Formfactor... no magnetic signal at high angles Polarisationfactor... only moment components normal.

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Presentation on theme: "Magnetic Diffraction Difference to nuclear scattering: Formfactor... no magnetic signal at high angles Polarisationfactor... only moment components normal."— Presentation transcript:

1 Magnetic Diffraction Difference to nuclear scattering: Formfactor... no magnetic signal at high angles Polarisationfactor... only moment components normal to κ contribute

2 Bestimmung von Formfaktoren: polarisierte Neutronen Formfaktor

3 Atomgitter Magnetisches Gitter Ferromagnet Antiferro- magnet Überstruktur - reflexe

4 In 1951 Shull showed the magnetic structure of the MnO crystal, which led to the discovery of antiferromagnetism (where the magnetic moments of some atoms point up and some point down). T N =122K

5 T N = 42 K M [010] T R = 10 K q = (2/3 1 0) Magnetic Structure from Neutron Scattering GdCu 2 Rotter et.al. J. Magn. Mag. Mat. 214 (2000) 281

6 Magnetic Diffraction using Laue Method (LADI – ILL) 4% Ga doped FeGe 2 This material undergoes a number of trans- itions and below 180K it locks into a non- harmonic spiral phase with a propagation vector of exactly 1/10. This gives rise to additional Bragg-peaks, which are shown in the second picture.

7 NdCu2

8 mehrere Kristallite (ca 120° verdreht) l τ 3τ3τ 5τ5τ

9 AF2 Pattern T=4.1K H=0T

10 NdCu2 Magnetic Structures at T=0

11 Pattern T=0 h AF1 F1 F2 F3 τ=( ) 5τ5τ3τ3τ τ=( ) τ=( ) 2τ2τ 2τ2τ 2τ2τ k

12 Komplexere Strukturen F2

13 |κ|[Å -1 ] I(κ) [counts] nichtkollineare Struktur(mcphase) GdCu 2 In


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