The magnetism of electrochemically delithiated Li-xNi1/2Mn3/2O-4 samples with space group P4(3)32 has been studied by dc-magnetization measurements. For the x = 1 sample, the temperature (T) dependence of the magnetization/field (= M/H) showed the appearance of a spontaneous magnetization below 130 K. Moreover, since a clear ferromagnetic (FM) M-H loop was observed at 5 K and its saturated magnetization (M-s) was almost equivalent to the predicted value (= 3.5 mu(B)), the whole sample was found to enter into a FM phase below 130 K (= T-C). A very similar FM behavior was also obtained for the x = 0.5 sample below 130 K, while the magnitude of M-s was almost a half of that for the x = 1 sample. In contrast to the x = 1 and 0.5 samples, M for the x = 0.05 sample increases almost linearly in the H range between similar to 5 and 55 kOe. Therefore, it is found that the fully delithiated Li-xNi1/2Mn3/2O-4 sample is in a paramagnetic or antiferromagnetic state even at 5 K.
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