Ferromagnetic resonance and nonlinear absorption in p-NPNN

Summary form only given. The FMR(Ferromagnetic Resonance) measurements have been performed on /spl beta/-phase p-NPNN(nitrophenyl nitronyl nitroxide) ferromagnetic below 0.6 K. We used an X-band resonance apparatus which can be used down to 0.5 K. We observed clear magnetostatic modes and non-linear line shapes for the as grown samples at the lowest temperature. We have also observed the effect known as the foldover effect. We should be careful about the demagnetization effect when the magnetization is large, therefore we performed the FMR measurement using nearly spherically shaped samples. We studied the temperature dependences of g-factor below 1.3 K, and found the intrinsically anisotropic behavior. This may be due to the anisotropy field along the crystal b-axis, which is consistent with the result reported by L.P. Le et at. using the /spl mu/SR measurement.