HIGH FIELD STUDY ON THE MAGNETIC MATERIALS OF LOW CHARACTERISTIC TEMPERATURE - Very Low Temperature Magnetization

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A Faraday force magnetometer has been developed for the static magnetization measurements at very low temperatures below 300mK and in fields up to 9T.The magnetic force acting on a specimen located in the adiabatic vacuum chamber of a dilution refrigerator is detected by a newly designed load-sensing variable capacitor. Use of a superconducting magnet with gradient coils enables an accurate measurement of a magnetic moment with a resolution of better than 1x10^<-7>Am^2(1x10^<-4>). A number of exlperiments have been done on heavy-electron systems.In CeB_6, a sharp magnetization jump has been found to develop below 0.5K at the phase II-phase III boundary [Bll(110)].In CePt_2Si_2, the (100) axis magnetization changes its slope at B-3T, however, no sharp metamagnetic transition has been observed down to 0.3K.In TmTe, an unusaul hysteresis has been found in the magnetization of the paramagnetic phase below 1.5K.We attribute this to an occurrence of quadrupolar ordering of the GAMMA_8 ground state of this compound around T-1.7K.