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

研制了一种法拉第力磁强计，用于在低于300mK的极低温度和高达9T的磁场中测量静态磁化强度。用新设计的负荷敏可变电容测量了作用在稀释式制冷机绝热真空室中样品的磁力。使用带有梯度线圈的超导磁体可以精确测量磁矩，分辨率优于1x10^-7；am^2(1x10^-4&gt；)。对重电子系统进行了大量的实验。在CeB_6中，在相II-相III晶界[BLL(110)]在0.5K以下发生了一个急剧的磁化跃变。在除CeB_2Si_2外，(100)轴的磁化强度在B-3T处改变了斜率，但在0.3K以下没有观察到急剧的变磁转变。在TmTe中，在1.5K以下的顺磁相的磁化强度出现了非索尔滞后。我们认为这是由于该化合物在T-1.7K附近发生了伽马_8基态的四极有序化。

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.