POSSIBLE DETERMINATION OF CRITICAL EXPONENTS FROM EXPERIMENTAL MAGNETIZATION DATA OF FERROMAGNETIC THIN-FILMS

The influence of finite-size effects on the determination of the criti cal exponent of the magnetization beta is critically discussed. We sho w that the usual fitting procedure, of fitting a power law to experime ntal data, is not correct for finite-size disturbed data and only acci dentally results in nearly correct values for the critical exponent. T he critical temperature resulting from a fit procedure is always too h igh, because the fitting range includes finite-size disturbed data. A new method is proposed, which circumvents the problems arising in fitt ing a power law to the experimental magnetization data. This method us es an effective critical exponent and allows the determination of beta and T-c even from finite-size disturbed data. The method will be reli able for evaluating experimental data in the currently interesting fie ld of confined magnetic films.