Spin waves magnetization

Fig. 130. Left ZF xSR spectrum of Ceo87Lao, 3Ri2Si2 together with the theoretical depolarization fimetion based on incommensurate sinusoidally modulated spin wave magnetic order (see text for details). From Yamamoto et al. (1997). Right Temperature dependence of the mean field seen by muons in magnetic Ce(R% jsRho ] 5)2 12 A single crystal oriented with the c-axis perpendicular to the muon beam was used. From Murayama et al.

Numerous experimental studies have shown that the magnetic hyperfine field of magnetic nanoparticles varies linearly with temperature at low temperatures, in accordance with (6.23). This is in contrast to bulk materials for which the decrease in the hyperfine field with increasing temperature in accordance with spin wave... 

Berger L (1996) Emission of spin waves by a magnetic multilayer traversed by a current. Phys Rev B 54 9353-9358... 

Interna] and external magnetic fields also play a special role for the observation of light scattering at magnons, as the quanta of spin waves are called - see Fig. 10. 

From the spin wave (or magnon) model of magnetic systems, the heat capacity versus temperature behavior below the ordering temperature is given192 by the following equation ... 

Figure 13. Spin-wave modes in nanowires (a) is the coherent mode (kL = 0) and (b) is of the curling type. When k l/R, then the perpendicular spin waves are essentially superpositions of plane waves exp(iA x) and t p( ikyy). Since the diameter of typical nanowires is much larger than interatomic distance, there are many excited perpendicular modes, and the finite-temperature magnetization MS(T) is reminiscent of bulk magnets.

Figure 13 shows various types of spin-wave modes in long nanowires. In very thin nanowires, where R < Rcoh, curling-type modes can be ignored [55, 114], and the perpendicular magnetization components obey Mx =... 

When large current densities (10+7 A/cm2) cross CPP spin valves, spin transfer effects start to be observed. When a spin polarized DC current flows across the CPP device, both well defined spin wave modes, and chaotic spin wave generation has been observed as a function of the injected DC current [65], These spin-wave modes lead to excess magnetic noise. These effects were first predicted by Berger [66] and Slonczewski [67], and have been now experimentally observed by several groups. At low frequencies, spin transfer effects also affect the CPP device transfer curve [68], and can be used to induce free layer switching in magnetoresistive devices. 

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