Pressure-induced incommensurate antiferromagnetic order in a ferromagnetic B -site ordered double-perovskite Lu2NiMnO6

Abstract

We have investigated the pressure effect on magnetic ordering of the ferromagnetic double perovskite ${\mathrm{Lu}}_{2}{\mathrm{NiMnO}}_{6}$ by magnetization, ac magnetic susceptibility, and neutron diffraction experiments up to 8.0 GPa in order to understand the ferromagnetic-to-antiferromagnetic phase transition by substitution of the $A$ sites in ${A}_{2}{\mathrm{NiMnO}}_{6}$ from rare-earth to indium or scandium ions. Strong ferromagnetic spin correlation seen in the susceptibility at low pressure is significantly suppressed by increasing pressure. In a neutron diffraction experiment, the magnetic Bragg reflections associated with ferromagnetic ordering disappear above 4.5 GPa. For the high-pressure region above 4.5 GPa, an antiferromagnetic ordering with long-period incommensurate modulation appears, which is coexistent with ferromagnetic short-range order. From mean-field calculations, we infer that pressure modification of the delicate balance of the competing next-nearest-neighbor exchange interactions between Ni and Ni, or Mn and Mn, plays an important role in the phase transition from ferromagnetic to antiferromagnetic ordering in ${A}_{2}{\mathrm{NiMnO}}_{6}$.