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 Lu2NiMnO6 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 A2NiMnO6 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 A2NiMnO6.