abstract: observation of the spin-flop transition of mnf2 by neutron diffraction
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Abstract: Observation of the spinflop transition of MnF2 by neutron diffractionG. P. Felcher, R. Kleb, and Vincent Jaccarino Citation: Journal of Applied Physics 50, 1837 (1979); doi: 10.1063/1.327190 View online: http://dx.doi.org/10.1063/1.327190 View Table of Contents: http://scitation.aip.org/content/aip/journal/jap/50/B3?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Effect of the spinflop transition on the Ni2+ fluorescence in MnF2 J. Appl. Phys. 49, 2195 (1978); 10.1063/1.324728 A Mechanical Model of the Spin-Flop Transition in Antiferromagnets Am. J. Phys. 39, 832 (1971); 10.1119/1.1986292 Mössbauer Spectroscopy Study of the SpinFlop Transition in FeDoped MnF2 J. Appl. Phys. 42, 1723 (1971); 10.1063/1.1660412 Antiferromagnetic Resonance in RbMnF3 below the SpinFlop Transition J. Appl. Phys. 37, 1132 (1966); 10.1063/1.1708366 Spin-Flopping in MnF 2 by High Magnetic Fields J. Appl. Phys. 32, S61 (1961); 10.1063/1.2000500
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Abstract: Spin dynamics in the linear antiferromagnet TMMC: Effect of a magnetic field at low temperature
J. P. Boucher and G. Jug
Centre d'Etudes Nucleaires de Grenoble. DRF/RM. 85 X 38041 Grenoble Cedex. France
F. Borsa
Istituto di Fisica e Unita GNSM del CNR. 27100 Pavia. Italy
PACS numbers: 64.60. - i. 76.90. + d, 05.40. + j. 75.20. - g
We present an investigation of the effect of an applied external magnetic field on the low temperature spin dynamics of the linear antiferromagnet (CH3)4NMnC13 (TMMC).
In zero external field the spectral density of the collective spin excitations is described by a relaxational peak centered at w=O for q~qc and a spin wave spectrum for q~q , where q is of the order of the inverse correlation l~ngth. InCthe presence of an applied field, the the relaxational peak is shifted to a frequency ~e while a gap is introduced in the spin wave dispersion relation. The dipolar anisotropy which was shown to be important below ~20K is taken into account in the present model. The effects of the applied field are included in the evaluation of ~e and of the different components of Ka
by referring to Villain's theory for low fields and extending the results at high field by means of a phenomenological treatment. The above description of the spin dynamics was utilized to compute the nuclear spin-lattice relaxation rate as a function of field and temperature The theoretical results without adjustable parameters are compared with experimental values obtained for H, D, and 14N in the field range 1-77kOe and in the temperature interval 1.5 - 4K. In high fields the comparison is satisfactory while at low fields there appears to be an extra contribution to the spin-lattice relaxation not included in the theory. The possible sources for the extra contribution are discussed.
Abstract: Observation of the spin-flop transition of MnF 2
by neutron diffraction G. P. Felcher and R. Kleb
Argonne National Lab .. Argonne, IlIinois 60439
Vincent Jaccarino
University of California, Santa Barbara, California 93106
PACS numbers: 75.50.Ee, 75.60.Ch, 61.12. - q
MnF2 is perhaps the most ideal example of uni~xial antiferromagnet. Below the Neel temperature the sublattice moments of Mn2+ are collinear to the tetragonal axis of the crystal, allowing two antiphase magnetic domains. If a suitable magnetic field is applied along the c-axis, the antiferromagnetically aligment moments flop in the basal plane of the crystal, with a sudden increase of the induced magnetization. At 4.2K, HSF = 92.7 KOe. In a polarized neutron experiment, the diffraction lines of the basal plane of a single crystal of MnF2 were studied as a function of an external field rather well aligned (0.2°) with the c-axis of the crystal. Above 92.7 Koe (at 4.2K) the magnetic response of the normal lattice lines increases suddenly as for an induced magnetization of 'V 0.4 J.lB/l1n.
At a slightly lower field the virgin diffraction runs of the superlattice reflections exhibit a sudden variation in the polarization-dependent intensity, indicating that the antiferromagnetic crystal locks into a single domain. The single domain state persists upon cycling of the field, enabling us to confirm the already observed l covalency effects on the density of Mn2+. In the spin flop state the polarization dependence of the intensities of the super lattice lines indicates that the magnetic moments lie largely in the basal plane. No new lines appear: the magnetic cell remains the same as in the low field state.
[1]. R. Nathans, H. A. Alperin, S. J. Pickart and P. J. Brown, J. Appl. Phys. 34, 1182 (1963).
1837 J. Appl. Phys. 50(3), March 1979 0021-8979/79/031837-01 $01.1 0 © 1979 American Institute of Physics 1837
[This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP:
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