Spin correlations in the ground state of NaSmMn2Ti4O12: A possible transition from high-temperature long-range ordered to low-temperature short-range correlated states

A new family of perovskite titanates NaRMn2Ti4O12 with R = Sm, Eu, Gd, Dy, Ho, Y has been recently obtained using high pressure synthesis. The members of the family crystallise into columnar quadruple-perovskite structure and show a long range magnetic order below 11-13K. Surprisingly, our previous neutron diffraction study revealed a second transition in Dy compound from high-temperature (T6K) ordered to low-temperature (T<6K) short-range correlated magnetic ground state. This is a very unusual transition, the nature of which is currently unclear. The aim of the present neutron diffraction experiment is to probe the long-range versus short range correlated ground state in the Sm perovskite which also shows two magnetic transitions on macroscopic measurements.

近期通过高压合成法获得了一类新的钙钛矿钛酸盐家族NaRMn₂Ti₄O₁₂（其中R=Sm、Eu、Gd、Dy、Ho、Y）。该家族成员结晶为柱状四重钙钛矿结构，且在11-13K以下呈现长程磁有序。令人意外的是，我们此前的中子衍射研究发现，镝化合物中存在二次相变：从高温（T≥6K）有序态转变为低温（T<6K）短程关联磁基态。这是一种非常罕见的相变，其本质目前尚不明确。本中子衍射实验的目的是探究钐钙钛矿中的长程与短程关联基态——该化合物在宏观测量中也显示出两次磁相变。