Cation distribution and magnetic properties of NixMn3-xO4-δ (x = 0.5, 0.75) synthesized by an ultrasound method. (November 2019)

• Record Type: Journal Article
• Authors: Alburquenque, D.; Troncoso, L.; Denardin, J.C.; Marco, J.F.; Gautier, J.L.
• Is Part Of: Journal of physics and chemistry of solids. Volume 134(2019)
• Page Start: 89
• Page End: 96
• Publication Date: 2019-11
• Subjects: Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2019.05.031
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: Manganese nickel oxides with a spinel-related structure, Ni x Mn3- x O4- δ (x = 0.5 or 0.75), were synthesized by an ultrasound-assisted sol-gel method. Inductively coupled plasma atomic optical emission spectroscopy and energy-dispersive X-ray spectroscopy analysis showed good agreement with the nominal oxide compositions. The Rietveld refinement of the X-ray data indicated that both Ni0.5 Mn2.5 O4- δ and Ni0.75 Mn2.25 O4- δ crystallize in the Fd 3 m space group, having cell parameter a of 0.8439 and 0.8392 nm, respectively. Scanning electron microscopy images showed agglomerated particles with sizes ranging from 300 nm to 1.4 μm, approximately. The magnetization curves showed paramagnetic behavior at room temperature, whereas ferromagnetic behavior was observed at 5 K. Zero-field-cooling and field-cooling magnetization measurements indicated the presence of three magnetic transitions, at T C = T 1 = 107 K, T 2 = 98 K, and T 3 = 54 K for Ni0.5 Mn2.5 O4-δ and at T C = T 1 = 101 K, T 2 = 93 K, and T 3 = 68 K for Ni0.75 Mn2.25 O4- δ . X-ray photoelectron spectroscopy analysis revealed the presence of Ni 2+, Mn 2+, Mn 3+, and Mn 4+ . The results provided by the different techniques allow us to propose the following cation distributions for these oxides: Mn 0.8 2 + Mn 0.2 3 + [ Ni 0.5 2 + Mn 1.04 3 + Mn 0.46 4 + ] O 3.98 2 − and Ni 0.03 2 + Mn 0.97 2 + [ Ni 0.72 2 + Mn 0.66 3 + Mn 0.62 4 + ] O 3.95 2 − . Highlights: We synthesized spinel oxides of the form Ni x Mn3- x O4- δ ( x = 0.5 or 0.75) were prepared using an UASG method for the first time. The complex magnetic structure resulting from the interaction between sublattices Ni 2+ -Mn 3+, Mn 2+ -Mn 3+, or Mn 3+ -Mn 4+ . By XRD, SEM-EDS, AAS, VSM, ZFC-FC and XPS measurements, the cation distributions were proposed as a function of composition.