The magnetic susceptibility of Si-inversion-layer electrons was measured for fields up to 15 T. Ideally, the system is expected to become totally quantized with discontinuous magnetization between discrete magnetic levels. In order to detect the small oscillatory magnetic signals (de Haas van Alphen effect), we have devised a geometry of a metal-oxide-semiconductor field-effect sample structure whose magnetic pickup is directly above the periphery of the gate electrode. The change of magnetization is provided by the modulation of the gate voltage. dMdns for Si(100) inversion layer was measured at 1.5 K for frequencies up to 100 kHz. The detected signals were found to have the expected frequency dependence and the expected spikes between magnetic levels. We also expect quantized steps characterized by integer units of double effective Bohr magneton (em*c) in each magnetic level, which has not been discerned so far with the present sensitivity of the measurements. © 1983 The American Physical Society.