On the n-p phase transitions in Mn1-x Cu x Cr2S4

The Seebeck coefficient for polycrystalline samples of: 1. Mn_1-x Cu _x Cr₂S₄ (0.0 ≤ x < 1.00) at 313 K and 2. MnCr₂S₄ between 313–393 K is presented. The electrical resistivity of Mn_1-x Cu _x Cr₂S₄ as a function of x at the room temperature is also presented. The n-p phase transition is observed in two cases: 1. on changing x at constant temperature (313 K) for 0.0 ≤ x ≤ 0.1 and 2. on changing temperature for MnCr₂S₄ at about 326 K. The first case is probably connected with the noncollinear ferromagnetic interaction of the chromium 3+ and 4+ ions. The second case follows from the strong ferrimagnetic interaction of the Mn²⁺ and Cr³⁺ ions in pure MnCr₂S₄.