2014/05/28 by Phillip T. Barton, Moureen C. Kemei, Michael W. Gaultois +5
Chemistry · Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Antiferromagnetism #Biology #Chemistry #Condensed matter physics #Context (archaeology) #Crystal structure #Crystallography #Heat capacity #Magnetic and transport properties of perovskites and related materials #Magnetism #Materials science #Multiferroics and related materials #Octahedron #Phase transition #Physics #Spinel #Tetragonal crystal system #Thermodynamics #cond-mat.mtrl-sci
paper · pdf · doi:10.1103/physrevb.90.064105
arxiv created 2014/05/28 · openalex publication_date 2014/08/08 · arxiv updated 2014/08/13 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
A structural phase transition from cubic Fd3m to tetragonal I41/amd symmetry with c/a> 1 is observed at TS=16 K in spinel GeCo2O4 below the N'eel temperature TN=21 K. Structural and magnetic ordering appear to be decoupled with the structural distortion occurring at 16 K while magnetic order occurs at 21 K as determined by magnetic susceptibility and heat capacity measurements. An elongation of CoO6 octahedra is observed in the tetragonal phase of GeCo2O4. We present the complete crystallographic description of GeCo2O4 in the tetragonal I41/amd space group and discuss the possible origin of this distortion in the context of known structural transitions in magnetic spinels. GeCo2O4 exhibits magnetodielectric coupling below TN. The related spinels GeFe2O4 and GeNi2O4 have also been examined for comparison. Structural transitions were not detected in either compound down to T\ensuremath≈8 K. Magnetometry experiments reveal in GeFe2O4 a second antiferromagnetic transition, with TN1=7.9 K and TN2=6.2 K, that was previously unknown and that bears a similarity to the magnetism of GeNi2O4.