Magnetic, transport, and electron magnetic resonance properties of Pr0.8Ca0.2MnO3 single crystals have been investigated. Two ferromagnetic transitions observed at TC1≈130 K and TC2≈60 K, denote a long range ordering of Mn and Pr spins, respectively, and exhibit an opposite pressure coefficient for TC, dTC1/dP≈0.24 K/kbar and dTC2/dP≈-0.75 K/kbar, respectively. The angular dependence of the magnetization in the (100) plane shows a strong twofold anisotropy, which increases under pressure. It was found that the resistivity ρ(T) obeys the Arrhenius law at 140 K<˜T<˜300 K with an activation energy Ea=130 meV, whereas below TC1, Ea=60 meV. The dynamic magnetoresistance vs magnetic field approaches a highest value of about 25% near TC1 for H=14.5 kOe. The dynamic resistance Rd exhibits a pronounced dependence on a bias current I at T<TC1. The results can be explained by the formation of orbital ordered states, which give rise to anisotropy and localization in the ferromagnetic insulating matrix. Electron magnetic resonance reveals coexistence of ferromagnetic metallic and insulating phases just below TC1. The signal of the metallic phase sharply drops in intensity at decreasing temperature. This effect is attributed to the formation of spin/cluster glass state. Possible mechanisms of current induced suppression of dynamic resistance in the ferromagnetic state are also discussed.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - 1 Jan 2003|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics