COLOSSAL MAGNETORESISTANCE AND RELAXATION PHENOMENA

The magnetization and magnetoresistance of La(1-x)A(x)MnO(3) (A = Sr, Ca) single crystals have been studied in the static regime. The same c haracteristics have been investigated as functions of time in response to a sharp change of the magnetic field, The magnetic moment M, dynam ic magnetic susceptibility chi', and resistivity rho are found to rela x noticeably in the samples with A = Sr (x = 0.3, 0.35). These paramet ers are shown to relax approximately logarithmically over time. The re laxation is temperature dependent, and diminishes when the temperature is far from that of the magnetic transition. The resistivity and magn etization do not relax when the field direction is reversed instantane ously. The static and relaxation properties observed are interpreted i n the framework of a simple phenomenological model.