Optical Spin Orientation in Ge-Based Heterostructures

Momentum Alignment and Spin Orientation of Photoexcited Electrons in GaAs in the Transition from Two- to Three-Dimensional Structures

Semiconductors ◽

10.1134/1.1379414 ◽

2001 ◽

Vol 35 (6) ◽

pp. 727 ◽

Cited By ~ 2

Author(s):

I. A. Akimov

Keyword(s):

Three Dimensional ◽

Spin Orientation

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Magnetism of Alkalitetrafluoromanganates (III) AMnF4 (A = K, Rb, Cs): Neutron Diffraction, Mössbauer and Magnetization Investigations

Zeitschrift für Naturforschung A ◽

10.1515/zna-1993-1102 ◽

1993 ◽

Vol 48 (11) ◽

pp. 1054-1072 ◽

Cited By ~ 4

Author(s):

Michel Molinier ◽

Christoph Frommen ◽

Werner Massa ◽

Jürgen Pebler ◽

Thierry Roisnel

Keyword(s):

Neutron Diffraction ◽

Magnetic Hyperfine Field ◽

Thermal Excitation ◽

Spin Orientation ◽

Domain Wall Dynamics ◽

Out Of Plane ◽

Exponential Temperature Dependence ◽

Jahn Teller ◽

Magnetic Spin ◽

Ordered Layers

Abstract The magnetic properties of the d4 Jahn-Teller systems AIMnIIIF4 with layered structures were investigated. Neutron diffraction on powders of KMnF4 and RbMnF4 revealed different antiferro-magnetic spin arrangements below TN = 4.5 K and 2.3 K, respectively: for KMnF4 canted antiparallel along a and b, for RbMnF4 parallel along a and antiparallel along b, in both cases parallel along c, the stacking direction of layers. Mössbauer investigations on 57Fe doped KMnF4 confirmed a spin orientation approximately within the layer plane. A discussion is given of the contributions to the magnetic hyperfine field and the Mössbauer linewidth in quasi-two-dimensional antiferromagnets with Ising anisotropy due to thermal excitation of domain wall dynamics (solitons). The experimental data seem to confirm the predicted exponential temperature dependence of the linewidth. From magnetization measurements on powders and a single crystal of KMnF4 the 2-d exchange energy and the out-of-plane and in-plane anisotropies could be extracted. In addition, from susceptibility measurements the exchange energies of NaMnF4 , RbMnF4 and CsMnF4 were calculated. A linear dependence of these exchange energies (positive for ferromagnetic CsMnF4 , negative for the other AMnF4 compounds) on the cos2 of the Mn-F-Mn bridge angle is observed and compared with the behaviour of the AFeF4 compounds which is also linear but with reverse sign of the slope. The specific superexchange mechanisms active in Jahn-Teller systems with antiferrodistortively ordered layers are suggested to be responsible for these findings.

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