First-order antiferromagnetic and structural transition in Sr-rich Pr1-xSrxMnO3

We present magnetization and resistivity data on polycrystalline samples of Pr1-xSrxMnO3 (0.58 less than or equal to x less than or equal to 1.00). All the samples are antiferromagnetic insulators at low temperatures. For 0.78 < x < 0.90, and for x = 0.58, both resistivity and magnetization show a clear hysteresis which indicates the first-order nature of the antiferromagnetic transition. Neutron diffraction data show that the paramagnetic-to-antiferromagnetic transition is accompanied by a cubic-to-tetragonal structural transition for 0.78 < x < 0.90, and tetragonal-to-orthorombic transition for x = 0.58. The other samples exhibit continuous transitions to the antiferromagnetic state. Our results show that the structural transitions are the origin of the discontinuous magnetic and resistive transitions. A moderate magnetoresistance effect can be observed for a lower Sr content possibly due to ferromagnetic fluctuations. (C) 2001 American Institute of Physics.