Detailed neutron study of the crossover from long-range to short-range magnetic ordering in(Nd1−xTbx)0.55Sr0.45MnO3manganites

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 ${({\mathrm{Nd}}_{1\ensuremath{-}x}{\mathrm{Tb}}_{x})}_{0.55}{\mathrm{Sr}}_{0.45}\mathrm{Mn}{\mathrm{O}}_{3}$ manganite compounds. The obtained results indicate that the ground state at $T=1.5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ is a long-range C-type canted ferromagnetic state for $0\ensuremath{\leqslant}x(\mathrm{Tb})\ensuremath{\leqslant}0.5$ with ferromagnetic domains larger than several hundreds of nm that decrease as the Tb content increases. In the concentration range $0.5\ensuremath{\leqslant}x(\mathrm{Tb})\ensuremath{\leqslant}0.6$, the ferromagnetic domain size decreases below $\ensuremath{\sim}100\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ and these large ferromagnetic clusters coexist in this concentration range with smaller short-range ferromagnetic clusters (around one nanometer size). For $x(\mathrm{Tb})\ensuremath{\geqslant}0.6$, only short-range ferromagnetic and A-type and C-type antiferromagnetic clusters are present and their size is below $\ensuremath{\sim}5\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. The obtained results are discussed in the context of the global phase diagram recently discussed for ${\mathrm{RE}}_{0.55}{\mathrm{Sr}}_{0.45}\mathrm{Mn}{\mathrm{O}}_{3}$ and in the context of the quantum critical point features recently suggested in manganites.