文摘
Effects of Pr substitution on the magnetic properties of perovskite manganite Nd0.5Sr0.5MnO3 havebeen investigated by measurements of electron spin resonance, magnetization, and powder neutrondiffraction. These experiments evidence a complex phase-segregated state at low temperatures andcoexistence of different ferromagnetic (FM) and antiferromagnetic (AFM) arrangements. Four temperatureregions are distinguished, similar for both studied samples Nd0.5-xPrxSr0.5MnO3 (x = 0.125, 0.25). Aroundthe room temperature and above there is a region of a single orthorhombic perovskite Ibmm phase ofparamagnetic (PM) state, where the first signatures for FM clusters can be indicated in the electron spinresonance spectra below ~1.1 TC (TC = 260 K). Between TC and TC2 (230 K for x = 0.25), a newtetragonal perovskite I4/mcm phase of FM long range order is formed at the expense of the PMorthorhombic phase. Below TC2, the FM order is established in both crystallographic phases, and theamount of the tetragonal phase for x = 0.25 achieves a maximum close to 45% of the sample. Finally,below ~160 K, strongly distorted perovskite domains with the CE and A-type kinds of AFM order (TN= 150 K for x = 0.25) are segregated while the orthorhombic FM phase quickly vanishes. At the lowesttemperatures, the two structurally distorted AFM domains make up 72% of the x = 0.25 sample, and theremaining 28% belongs to the tetragonal FM domains.