Change of the Magnetic Moment and Specific Heat of La_0.9Ca_0.1MnO₃ after Heat Treatment in Oxygen and Argon

Magnetic moment and specific heat of La0.9Ca0.1MnO3 after heat treatment in oxygen and argon were studied. It is found that the sample after oxygen treatment has higher magnetic moment and specific heat than that after argon treatment. The difference of specific heat between the samples after oxygen treatment and after argon treatment has linear relationship with T3/2. The heat treatment in oxygen and argon would induce the change of oxygen density which effect the magnetic moment and specific heat. For EPIR effect, the increase of ferromagnetic regions induced by oxygen motion driven by electric pulses would increase the magnetic moment and specific heat, and the different of specific heat between low resistance state and high resistance state has linear relationship with T3/2. According to oxygen motion driven by electric pulses model, the low resistance state has higher oxygen density than high resistance state. It implies that the increase of magnetic moment and specific heat with resistance decreasing may arise from the oxygen motion driven by electric pulses for EPIR effect.