  We present an extensive study of the time dependence of the magnetization in
a polycrystalline and low temperature charge ordered La0.5Ca0.5MnO3 sample.
After application and removal of a 5 T magnetic field, a systematic variation
of the magnetic relaxation rate from 10 K to 245 K was found. At 195 K, the
magnetization decreases in a very short time and after that it increases slowly
as a function of time. Moreover, between 200 and 245 K, an increase in
magnetization, above the corresponding value just after removing the 5 T
magnetic field, was measured. This unusual behavior was tested in several other
relaxation procedures. PACS: 70, 74.25 Ha, 75.60.-d, 76.60.Es
