Permanent magnetic moment in mesoscopic metals with spin orbit interaction

We argue that at zero temperature an isolated metal particle (or an AB ring) with spin-orbit interaction and odd number of electrons will have a permanent magnetic moment, even in zero magnetic field (flux). In a zero-field-cooled state both the direction and the magnitude of the moment varies from particle to particle and averages to zero. In a field-cooled state it averages to ∼ μ_B( k_Fℓ) ^1/2. We argue that the permanent moment is due to an uncompensated electron in the last occupied (Fermi) level. We introduce an effective single-electron Hamiltonian which accounts for spin-orbit coupling.