Ferrimagnetism and spin excitation in a Ni–Mn partially inverted spinel prepared using a modified polymeric precursor method

• Ni–Mn oxide partially-inverted spinel made by modified polymeric precursor method.
• Magnetic measurements showed a ferrimagnetic and a parasitic magnetic transition.
• NPD revealed a magnetic structure consistent with a star-like moment arrangement.
• INS measurements indicated four distinct temperature-dependent magnetic regimes.

We demonstrate that a Ni–Mn oxide partially inverted spinel (Ni1−νMnν)[NiνMn2−ν]O4 having inversion degree ν   ≈ 0.8 and produced by a modified polymeric precursor method exhibits behaviour previously reported only in monophased samples. The structure of the specimen was determined using Rietveld analysis of X-ray and neutron powder diffraction data, showing that at room temperature the material crystallizes in the Fd3¯m space group with a lattice constant a = 8.392 Å. Combining magnetization measurements with neutron powder diffraction, we show that the magnetic structure of this spinel is associated with the interplay between the ferromagnetic and antiferromagnetic lattices which coexist due to the cations' presence on both tetrahedral and octahedral sites. Our analysis of the neutron diffraction data confirms the postulated magnetic structure involving a star-like moment arrangement, arising from competition for the B (octahedral) spinel sites by the Ni and Mn cations. Finally, we show that strong magnetic fluctuations are observed in the inelastic neutron scattering data.