First-order antiferromagnetic and structural transition in Sr-rich Pr[sub 1-x]Sr[sub x]MnO[sub 3].

We present magnetization and resistivity data on polycrystalline samples of Pr[sub 1-x]Sr[sub x]MnO[sub 3] (0.58≤x≤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. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]