High magnetic field studies of 3d and 4f magnetism in (R0.7A0.3)MnO3:: R = La3+, Pr3+, Nd3+, A = Ca2+, Sr2+, Ba2+, Pb2+

Magnetization curves up to 25 T at 4.2 K are reported for mixed-valence manganites (R(0.7)A(0.3))MnO3. All the R = La compounds show an extrapolated ferromagnetic moment of similar to 3.4 mu(B)/f.u. The A = Sr and Ca compounds show essentially no high-field slope, dM/dB <0.001 mu(B)/T whereas the Pb and Ba compounds show slopes of 0.0047 and 0.0025 mu(B)/T, suggesting that electrons of both spins are present at the Fermi level. All Pr compounds show much greater slopes, dM/dB approximate to 0.02 mu(B)/T associated with a singlet ground state for Pr3+. All except the Ca compound have extrapolated moments of 3.6 +/- 0.3 mu(B)/f.u. but (Pr0.7Ca0.3)MnO3 exhibits two first-order magnetization processes, at 5 and 6 T, due respectively to melting of charge order as the compound becomes ferromagnetic and a level-crossing transition for the Pr3+ ion. All the Nd compounds, except for the charge ordered, Ca containing compound, have a magnetization which is similar to 1 mu(B) greater than their La counterparts, due to ferromagnetic alignment of Nd and Mn moments. (C) 1999 American Institute of Physics. [S0021-8979(99)74008-9].