Spin wave spectrum

Spin-Wave Spectrum in the Presence of Spin Vortices The Origin of an Hourglass-Shaped Magnetic Excitation Spectrum... 

Clearly the integration f dk/k resulting from eq. (68) as k - 0 would yield a logarithmic divergence, which already suggests that (without a stabilizing field or anisotropy that would induce a gap into the spin wave spectrum) there cannot be a spontaneous magnetization,... 

The properties of the spin waves (magnons) in heavy lanthanide metals have been reviewed recently by Mackintosh and M0ller (1972). In the ferromagnetic state the spin wave spectrum of an isotropic spin system with long range interaction has the form... 

Fig. 4. Constant-energy scans through the counter-propagating spin wave modes of LajCuO. Using higher-energy neutrons available at a hot source , it is possible to measure the spin waves at frequencies where the two branches emerging from (100) and equivalent positions are separable, allowing a determination of the spin wave velocity. The dashed line in the upper scan shows the resolution-limited response, while the solid curves are the results of fits to a resolution-convolved spin wave spectrum with a velocity of 850meVA. From Hsqrden et al. (1990).

Fig. 89. Schematic constant-Q spectra of the magnetic response for the reentrant spin-glass problem. Dotted line represents spin-wave spectrum when the coupling between FM and SG network vanishes dashed line represents spectrum for SG network, and solid line corresponds to spectra for FM network when it is coupled to SG spins (from Shapiro et al. 1986).

Hiraoka etal. [10] discuss the zero point effect of the magnetic dipolar interaction described by Holstein, Primakoff [11] as a possible mechanism of the reduction in the ferromagnetic moment at 0 K (see pp. 214, 216). The estimated high dipolar interaction suggests that it has an appreciable influence on the low temperature spin wave spectrum and in pressure-induced ferromagnetic EuSe, probably also causes a deviation of the NMR-v(T) dependence from the law at T/Tc< 1. This is expected to occur somewhere below 1.7 K [10]. 

Ref [30] during the analysis of spin-wave spectrum in LaMnO, . We arbitrarily (not having experimental data) assumed K2=. 92K. If one uses data on Neel temperature for [5, 38] we shall put approximately = I4 = S.7K. Keeping in mind the results of papers [5, 34-38] let s put some mean experimental values for transition concentrations X3 = 0.2,X4 = 0.5,Xg = 0.7,Xj = 0.85. When substitute these ten parameters... 

Fifth, note that, in our model an energy gap in spin-wave spectrum appears due to both anisotropy and (quadratic and double) exchange energies, which is caused by the presence of ions with different S,S +1/2) spins in the system. 

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