Spin-reorientation transition at isoelectronic substitution in double-layer manganites (La1-zPrz)(1.2)Sr1.8Mn2O7

The transport, magnetic, and thermal properties of single crystal double-la yer manganites of the Ruddlesden-Popper series (La1-zPrz)(1.2)Sr1.8Mn2O7(z = 0.1 or 0.4) were studied. The compounds exhibit the colossal negative mag netoresistance effect in the region of a transition into a ferromagnetic st ate. Upon the isoelectronic substitution of Pr3+ for La3+, the Curie temper ature decreases, while the easy magnetization axis rotates from the ab plan e to the c axis. The observed effect is related to a change in the occupanc y of d(x)(-y)(2)(2) and d(3z)(-r)(2)(2) orbitals as a result of stretching of the MnO6 octahedra. (C) 2001 MAIK "Nauka/Interperiodica".