About cookies on this site Our websites require some cookies to function properly (required). In addition, other cookies may be used with your consent to analyze site usage, improve the user experience and for advertising. For more information, please review your options. By visiting our website, you agree to our processing of information as described in IBM’sprivacy statement. To provide a smooth navigation, your cookie preferences will be shared across the IBM web domains listed here.
Paper
Study of far-infrared excitations in metamagnetic FeCl2 2H2 O
Abstract
The spin-wave spectra in the antiferromagnetic, ferrimagnetic, and ferromagnetic phases of FeCl2 2H2O have been examined at 2 and 6°K. These spectra are well described by a spin-wave calculation; it is shown that g=2.230.02, S=2, and that the exchange interactions are isotropic. The (large) longitudinal anisotropy is included in the Hamiltonian as a single-ion anisotropy (D=+9.580.05 cm-1), which is shown to make an anomolously large contribution to the spin-wave energies. These results are discussed and interpreted from the point of view of crystal-field theory. In all three metamagnetic phases, the magnetic resonance modes are observed to interact with a field-independent excitation with energy 31.5 cm-1, which is presumably an optical phonon. The measured value of the metamagnetic transition field Hc2=45.00.5 kOe compares quite well with Narath's value of 45.6 kOe, but our value of Hc1=35.00.5 kOe is in poor agreement with Narath's 39.2 kOe. Near Hc1 (the antiferromagnetic-to-ferrimagnetic transition field), the far-infrared spectrum appears to indicate that both antiferromagnetic and ferrimagnetic "domains" coexist over a certain range of field. The temperature dependence and hysteresis of these domains are also described and compared with Tinkham's microscopic description of these transitions. © 1970 The American Physical Society.