Scaling Behavior of the Magnetization of Insulating Si:P

We report measurements of the magnetization of insulating phosphorus doped silicon for fields up to 50 kG and temperatures down to 1.25K, for dopant concentrations n=6.7x10(17) cm(-3) to N=2.8x10(18) cm(-3). A comparison of the data is made with a generalization, to finite fields, of a scaling calculation of the magnetic properties of the insulating phase, and implies that the model of hierarchically coupled spin pairs is quantitatively accurate.