Electron paramagnetic resonance in the low dimensional antiferromagnets CsMnCl3 · 2H2O and BaMnF4

We have studied the EPR spectrum of the quasi-one-dimensional system CsMnCl3 · 2H2O and quasi-two-dimensional BaMnF4 over a wide range of temperatures. In the immediate neighborhood of the Néel point a change is observed in the character of the critical broadening of the resonance line (a crossover), which indicates a change in the spin dynamics of these low dimensional systems. We discuss possible reasons for the change in the dynamics related to the influence of the weak exchange and interion anisotropy. It is shown that these mechanisms do not provide a quantitative description of the effect. We have studied the angular dependence of the width and shape of the resonant absorption line at low and high temperatures. In the EPR spectrum of CsMnCl3 · 2H2O a half-field satellite line is observed. These results are interpreted on the basis of models for the one- and two-dimensional structures, respectively, taking into account the changes in the spatial and temporal characteristics of the correlation functions.

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