The normal spinel oxide MgCr2 O4 is cubic at room temperature while the normal spinel CuCr2 O4 is tetragonal as a consequence of the Jahn-Teller activity of Cu2⊃+ on the tetrahedral sites. Despite different end-member structures, a complete solid solution of Mg1-x Cux Cr2 O4 can be prepared with compounds of composition x=0.43 displaying a first-order phase transition at room temperature. Reverse Monte Carlo analysis of total neutron scattering on data acquired between 300 and 15 K on samples with x=0.10, 0.20, and 0.43 provides unbiased local and average structure descriptions of the samples, including an understanding of the transition from local Jahn-Teller distortions in the cubic phase to cooperative distortions that result in a tetragonal structure. Distributions of continuous symmetry measures help to understand and distinguish distorted and undistorted coordination around the tetrahedral site in the solid solutions. Magnetic exchange bias is observed in field-cooled hysteresis loops of samples with dilute Cu2⊃+ concentration and in samples with tetragonal-cubic phase coexistence around 300 K.
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Dec 10 2010|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics