We discuss the possibility of magnetic instability in a system of metallic grains in the presence of disorder. We demonstrate that depending on the geometry of the grain (quasi-two dimensional, three dimensional etc) a disordered system may exhibit a finite temperature partial spin polarization even if its clean analog is paramagnetic. The disorder and temperature dependent magnetization and spin susceptibility are calculated. It makes it possible to determine conditions for Spin Blockade and Spin Anti-Blockade in granular media. We discuss the influence of mesoscopic fluctuations in isolated grain on dynamic spin susceptibility and possible ways to determine the microscopic parameters of spin-spin interaction by inelastic neutron scattering experiments.
Ludwig-Maximilian University, Munich, Germany