DC-magnetization measurements on electrochemically delithiated Lix[Ni1/2Mn3/2]O4

The magnetism of electrochemically delithiated Lix[Ni1/2Mn3/2]O4 samples with space group P4332 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 (Ms) was almost equivalent to the predicted value (=3.5μB), the whole sample was found to enter into a FM phase below 130 K (=TC). A very similar FM behavior was also obtained for the x=0.5 sample below 130 K, while the magnitude of Ms 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 ∼5 and 55 kOe. Therefore, it is found that the fully delithiated Lix[Ni1/2Mn3/2]O4 sample is in a paramagnetic or antiferromagnetic state even at 5 K.