Interplay Between Cation Distribution and Magnetic Properties in MgM 0.5 Mn 1.5 O 4 (M = Al, Ga) and Al 1.5 Mn 1.5 O 4 S
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ORIGINAL PAPER
Interplay Between Cation Distribution and Magnetic Properties in MgM0.5Mn1.5O4 (M = Al, Ga) and Al1.5Mn1.5O4 Spinels Boubker Mehdaoui 1
&
Abdeslam El Bouari 1
Received: 6 June 2020 / Accepted: 30 July 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The polycrystalline samples of Al1.5Mn1.5O4, MgAl0.5Mn1.5O4 and MgGa0.5Mn1.5O4 were prepared using a standard ceramic method and characterized by X-ray diffraction and magnetic measurements. The cationic distributions were determined by the combination of the Rietveld refinement and the tabulated cation-oxygen distances in spinel compounds. The results obtained were compared with those calculated using a thermodynamic calculation according to the O’Neill model. The Al1.5Mn1.5O4 compound is characterized by its cationic distribution with a high occupancy rate of the magnetic ions Mn2+ in the A sites, in agreement with the experimental magnetic moment. This compound presents a ferrimagnetic behavior at T < 23.5 K. The MgAl0.5Mn1.5O4 and MgGa0.5Mn1.5O4 compounds have almost the same distribution of magnetic manganese cations in both A and B sites, with a weak presence of the magnetic ions Mn2+ in the A sites, justified by the refinement Rietveld, thermodynamic calculation and the hyperbolic form of the inverse magnetic susceptibility above 23.2 K. Both compounds have almost the same magnetic behavior at low temperature T < 23.2 K, typical of a spin glass. This behavior is attributed to the strong presence of diamagnetic ions on the A sites and the magnetic disorder in B sites. Keywords Spinel . Cation distribution . Thermodynamic calculation . Ferrimagnetism . Spin glass
1 Introduction Spinel oxides with general formula AB2O4 constitute a technologically important class of metal oxides [1]. They crystallize in a cubic system with space group symmetry of Fd-3m. The oxygen ions are located in the 32e position; the tetrahedral sites (A) are in 8a positions, while the octahedral sites (B) are in the 16d positions. The B sites form a pyrochlore network of tetrahedrons linked by their vertices [2], and the A sites form a diamondlike network [3]. Due to their multiple compositions and electronic configurations, spinels have presented different fundamental and interesting chemical and physical properties such as electronic, optical, electrical, and catalytic properties [4]. Particularly, spinels have demonstrated various magnetic properties [1]. This diversity is associated with the wide variety of cation substitutions that can be made in tetrahedral (A) and * Boubker Mehdaoui [email protected] 1
Faculty of Sciences Ben M’Sik, Laboratory of Physical-Chemistry of Applied Materials, University Hassan II of Casablanca, Avenue Idriss El Harti, B.P. 7955 Casablanca, Morocco
octahedral (B) sites leading to a number of interesting magnetic properties such as ferrimagnetic [5], ferromagnetic [6], antiferomagnetic [7], magnetic frustration [8], and/or multiferroicity [9]. These compounds continue to interest scientists, for
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