In:
Zeitschrift für Naturforschung A, Walter de Gruyter GmbH, Vol. 48, No. 11 ( 1993-11-1), p. 1054-1072
Abstract:
The magnetic properties of the d 4 Jahn-Teller systems A I Mn III 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 antiparallel 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 experimental 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.
Type of Medium:
Online Resource
ISSN:
1865-7109
,
0932-0784
DOI:
10.1515/zna-1993-1102
Language:
English
Publisher:
Walter de Gruyter GmbH
Publication Date:
1993
detail.hit.zdb_id:
2079610-9
detail.hit.zdb_id:
124634-3
detail.hit.zdb_id:
124633-1
detail.hit.zdb_id:
2767412-5
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