Detailed neutron study of the crossover from long-range to short-range magnetic ordering in (Nd_1-xTb_x)_0.55Sr_0.45MnO₃ manganites

Abstract

We have applied three complementary neutron techniques (neutron diffraction, neutron depolarization, and small-angle neutron scattering) to investigate the crossover from long-range to short-range magnetic ordering in (Nd_1-xTb_x)_0.55Sr_0.45MnO₃ manganite compounds. The obtained results indicate that the ground state at T = 1.5K is a long-range C-type canted ferromagnetic state for 0⩽x(Tb)⩽0.5 with ferromagnetic domains larger than several hundreds of nm that decrease as the Tb content increases. In the concentration range 0.5 ⩽ x(Tb) ⩽ 0.6, the ferromagnetic domain size decreases below ∼100nm and these large ferromagnetic clusters coexist in this concentration range with smaller short-range ferromagnetic clusters (around one nanometer size). For x(Tb) ⩾ 0.6, only short-range ferromagnetic and A-type and C-type antiferromagnetic clusters are present and their size is below ∼5nm. The obtained results are discussed in the context of the global phase diagram recently discussed for RE_0.55Sr_0.45MnO₃ and in the context of the quantum critical point features recently suggested in manganites.