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1996 (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    T. Myojin, T. Ohno, K. Mizuno, A. Tsujimura, K. KojimaRequires cookie*
 Title    Spin Reorientation Phenomena in (Rj^R^Co^B Compounds  
 Abstract    The variation of NMR spectra and magnetization with temperature in (Rj _ x R^) 2 Co 14 B (R = Y or Gd. R' = Tb. Dy or Ho 0 < .v < 1) have been measured. These compounds undergo spin reori-entation at a temperature T SR when Y and Gd are substituted by Tb, Dy and Ho, and the temperature T SR increases with the fraction x. Phase diagrams of spin arrangement in these systems have been obtained. The results are discussed from the view point of competition between the crystalline electric field and the Co-R exchange interaction. 
  Reference    Z. Naturforsch. 51a, 726—730 (1996); received November 20 1995 
  Published    1996 
  Keywords    R 2 Co 14 B, Spin reorientation, Magnetic anisotropy, NMR, Magnetization 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0726.pdf 
 Identifier    ZNA-1996-51a-0726 
 Volume    51