Magnetic transitions in Cu2−xSe below room temperature

Abstract We have measured the magnetic susceptibility, resistivity, magnetoresistivity and Hall effect of nonstoichiometric cuprous selenide between 5 and 350 K. Our results show that below 170 K Cu 2− x Se is a mixture of diamagnetic Cu 1.995 Se and paramagnetic Cu 3 Se 2 . The phase diagram of the Cu–Se system, in which 170 K represents the eutectic isotherm, governs the relative content of the two phases. For the Cu 3 Se 2 phase a transition to an antiferromagnetic state is observed at about 50 K, with the corresponding Weiss temperature Θ =120 K. On heating above 170 K Cu 2− x Se becomes completely diamagnetic, but the transformation is slow and strongly time dependent. The complicated magnetic behaviour is ascribed to a broad temperature hysteresis of the process.