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1999 (1)
1993 (1)
1Author    Michel Molinier, Christoph Frommen, Werner Massa, Jürgen Pebler, Thierry RoisnelRequires 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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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-1054.pdf 
 Identifier    ZNA-1993-48a-1054 
 Volume    48 
2Author    J. Pebler, C. Frommen, M. Mangold, W. TreutmannRequires 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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 TEI-XML for    default:Reihe_A/54/ZNA-1999-54a-0317.pdf 
 Identifier    ZNA-1999-54a-0317 
 Volume    54