Magnetic relaxation in condensed matter

Abstract

The study of the Nuclear Magnetic Resonance enables people to enhance their knowlwdge on scientific phenomena. For its use, many examples can be given such as in Solid State Physics, it may be used to have more information about the bulk system, in Organic Chemistry, one uses NMR for the analysis of complex molecules and so on. This work is a reformulation and unification of the various theories of magnetic relaxation and magnetic resonance. We start off our discussion on the magnetic relaxation theory with an introductory explanation of the Bloch Equations and the relaxation processes. It is preceeded with a quantum-mechanical treatment introducing the density matrix. A quantum mechanical theory of frequency dependent susceptibilities of magnetic systems is examined with the case of linear theory which assumes that the external disturbance is always small and the response of the system to it is linear. The method used to calculate the relaxation function is quantum-statistical. We computed the line contour of resonance absorption by using the Fourier integral method. (Chapter III)In the following chapter, the physical meaning of the reduced density matrix is discussed. Its usefulness is to obtain all the information necessary to evaluate the expectation value.We continue our discussion with the theory of NMR in homo-genous adsorbed systems for two dimensional systems. It is shown that the reduced dimensionality has the effect of decreasing the relaxation times. With the Pulse NMR technique, we measured the relaxation times around 0°C and presented our results in the last chapter. The comparison of the result was made with the PPP people's result.