Abstract
In order to obtain information about the magnetic moment of CuCr 2Se 4 and the changes in the Curie point, we have investigated the magnetic structure and the temperature dependance of the magnetic susceptibility. Neutron diffraction experiments were done on the powder of a CuCr 2Se 4 sample both at 10 K and at 295 K. The magnetic measurements were done in the temperature range 295–720 K. CuCr 2Se 4, which crystallizes in the normal spinel structure, is a collinear ferromagnetic. The obtained magnetic moment μ(Cr)=2.81 μ B (at 10 K) and the interatomic distances indicate that in the ferromagnetic phase chromium is in the oxidation state between +3 and +4. On the other hand, the effective magnetic moment μ eff(Cr)=4.4 μ B, obtained from the susceptibility measurements in the paramagnetic phase, corresponds to chromium in an oxidation state between +2 and +3. The spin value, assuming a quenched moment, is S=1.40 and S=1.75 in the ferromagnetic and in the paramagnetic phase, respectively. At the Curie point, T C=450 K, the phase transition of the first order with the change of magnetic moment and valence of the chromium ion takes place.
Published Version
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