Spin Waves and Spin Relaxation in Normal Fermi Liquids.
This work explores several aspects of spin-dependent excitations in normal Fermi liquids. Chapter 1 is a general introduction and overview of the work. The Landau kinetic equation and its application to nonequilibrium proper- ties of Fermi liquids is discussed, and the properties of collective density modes are briefly reviewed. The properties of both longitu- dinal and transverse spin excitations are then outlined, leading up to a discussion of spin waves and spin diffusion, including the Leggett -Rice effect. Chapter 2 discusses the possibility of making a determination of the contribution of many-body interactions to the large effective mass in "heavy-fermion" materials, e.g. UPt(,3), by the method of conduction-electron spin resonance (CESR). It is shown that a microwave trans- mission observation of CESR might show a resonance pattern which, based on already measured parameters, would clearly distinguish among various suggested models for the strength of the many-body effects. Chapter 3 investigates the accuracy of the usual relaxation time approximations, involving the spin diffusion lifetime (tau)(,D), which are generally made in analyses of spin waves and the Leggett-Rice effect in Fermi liquids. By employing the variational methods of Ah-Sam, H(SLASHCIRC)jgaard -Jensen and Smith, and Egilsson and Pethick, we are able to determine upper and lower bounds on the effective diffusion coefficient resulting from spin wave phenomena which are accurate in the whole Fermi liquid regime. Our results indicate that the usual approximations break down for(' )T < 7 mK in ('3)He, but are accurate to within (TURN)2% in 5% ('3)He-('4)He mixtures. Chapter 4 contains a calculation of the longitudinal spin relaxa- tion time T(,1) in bulk ('3)He in the Fermi liquid (T << T(,F)) regime. The kinetic equation is used to obtain an expression for T(,1) in terms of perturbations of the scattering amplitude. These perturbations are then obtained using the induced interaction model. Our results are in good agreement with experiment, as well as with previous calculations.
- Pub Date:
- Physics: Condensed Matter