| | 1 | Author
| Michel Molinier, Christoph Frommen, Werner Massa, Jürgen Pebler, Thierry Roisnel | Requires cookie* | | | Title
| Magnetism of Alkalitetrafluoromanganates (III) AM11F4 (A = K, Rb, Cs): Neutron Diffraction, Mössbauer and Magnetization Investigations  | | | | Abstract
| The magnetic properties of the d 4 Jahn-Teller systems A'Mn m F 4 with layered structures were investigated. Neutron diffraction on powders of KMnF 4 and RbMnF 4 revealed different antiferro-magnetic spin arrangements below T N = 4.5 K and 2.3 K, respectively: for KMnF 4 canted antiparal-lel along a and b, for RbMnF 4 parallel along a and antiparallel along b, in both cases parallel along c, the stacking direction of layers. Mössbauer investigations on 57 Fe doped KMnF 4 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 experimen-tal data seem to confirm the predicted exponential temperature dependence of the linewidth. From magnetization measurements on powders and a single crystal of KMnF 4 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 NaMnF 4 , RbMnF 4 and CsMnF 4 were calculated. A linear dependence of these exchange energies (positive for ferromagnetic CsMnF 4 , negative for the other AMnF 4 compounds) on the cos 2 of the Mn-F-Mn bridge angle is observed and compared with the behaviour of the AFeF 4 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. | | | |
Reference
| Z. Naturforsch. 48a, 1054—1072 (1993); received September 17 1993 | | | |
Published
| 1993 | | | |
Keywords
| Neutron diffraction, Mössbauer effect, Magnetization, Exchange and anisotropy energy | | | |
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| default:Reihe_A/48/ZNA-1993-48a-1054.pdf | | | | Identifier
| ZNA-1993-48a-1054 | | | | Volume
| 48 | |
| 2 | Author
| J. Pebler, C. Frommen, M. Mangold, W. Treutmann | Requires cookie* | | | Title
| Magnetic Susceptibility Calculated from Correlation-Lengths Derived by Mössbauer Relaxation Spectra | | | | Abstract
| From the knowledge of the spin correlation functions derived from Mössbauer relaxation spectra of quasi-one-dimensional A 2 MnoyxFe ()() 2F< i (H20) we could fit the antiferromagnetic susceptibilities of A 2 MnF 5 (H 2 0) with A = Na , (NH 4) + , K + , Rb + obtained for single crystal samples. The calculation yielded characteristic parameters such as the local anisotropy D, the intra-chain exchange energy J, the inter-chain exchange energy \ J'\, the Neel temperature T N , and the spin canting angle (p. | | | |
Reference
| Z. Naturforsch. 54a, 317—328 (1999); received March 17 1999 | | | |
Published
| 1999 | | | |
Keywords
| Mössbauer Relaxation Spectra, Non-linear Excitations (Magnetic Solitons), 1-d Correla-tion Length, Exchange and Anisotropy Energy, Antiferromagnetic Order, Weak Ferromag-netism | | | |
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| default:Reihe_A/54/ZNA-1999-54a-0317.pdf | | | | Identifier
| ZNA-1999-54a-0317 | | | | Volume
| 54 | |
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