Dipolar Anisotropy of Spinwaves in the Isotropic Ferromagnets {{EuS}} and {{Pd2 MnSn}}

The spin excitations in the model Heisenberg ferromagnets EuS and Pd2MnSn have been investigated below Tc using polarized-neutron scattering. In EuS the spin waves with transverse polarization with respect to q (8 Slq) renormalize near Tc as expected according to dynamical scaling theory, and the excitations have a gap with A 20.040 meV. In contrast, the longitudinal spin waves (8 S IIq) are possibly damped. These observations are clearly related to the strong dipolar anisotropy that has already been observed above Tc. Similar investigations in Pd2MnSn show, that the spin waves are independent of the polarization within the q-range investigated. This result confirms that the dipolar interactions in Pd2MnSn are indeed small.     «

The spin excitations in the model Heisenberg ferromagnets EuS and Pd2MnSn have been investigated below Tc using polarized-neutron scattering. In EuS the spin waves with transverse polarization with respect to q (8 Slq) renormalize near Tc as expected according to dynamical scaling theory, and the excitations have a gap with A 20.040 meV. In contrast, the longitudinal spin waves (8 S IIq) are possibly damped. These observations are clearly related to the strong dipolar anisotropy that has already...     »