Electron Spin Resonance in the Paramagnetic and Magnetically Ordered States

9 Electron Spin Resonance in the Paramagnetic and Magnetically Ordered States 

AHhki is the linewidth measured for a magnetic field applied along crystallographic directions (hkl) or planes (hkl). 

The field for resonance is ca. 12.7, 8.7, and 7.5 kOe at the microwave frequencies used, 35.25, 24.0, and 21.48 GHz, respectively, well above the critical internal field H2. Thus, EuSe may be assumed to be in the ferromagnetic state below the Neel temperature (Tn = 4.6 K). The field for resonance is ca. 6.4 and 3.2 kOe at the lower frequencies 18.26 and 9.05 GHz, respectively. Under these conditions, EuSe is magnetically ordered below T but not ferromag-netically, see p. 206. 

The temperature dependence of AH(no) at 24 GHz in the paramagnetic state down to the maximum near 12 K is the same for annealed stoichiometric EuSe and for as-grown Eu-rich 

The observed angular dependence of AH is not simply related to the angular dependence of the anisotropy energy. The existence of domains and of crystallographic distortions in the volume of the domain walls could cause two-magnon disorder scattering and, hence, further anisotropic contributions to the linewidth [6]. 

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