Giant negative magnetoresistance in the vicinity of the ferromagnetic phase transition TC in Sm0.55Sr0.45MnO3

The temperature dependence of the resistance in Sm0.55Sr0.45MnO3 at zero magnetic field and its first derivative served for the determination of TC which turned out to be equal to 129.1K. Then, the resistance measurements were carried out as functions of the stationary magnetic fields up to 14T at the following temperatures: 118.6, 124.6, 133.6 and 139.7K. Two of them are below and two of them are above TC. It turned out that at all the four temperatures the resistance reveals a hysteresis. It turned also out that the closer the temperature to TC the greater this hysteresis. At all the four temperatures the magnetoresistance is negative, its absolute value depends on the magnetic field and reaches 100% at 12T. At lower fields the absolute value of the negative magnetoresistance increases monotonically with the decrease of temperature starting from 139.7K. On the other hand, a maximum observed on all the primary and secondary curves above TC moves with the decrease of temperature towards the lower magnetic fields and disappears on all the curves below TC. On the secondary curves above TC this maximum is flat.