Ferromagnetic semiconductors: Magnetic properties of the pyrochlores, (YxLu1−x)2V2O7 and (ScxLu1−x)2V2O7

Some magnetic properties of eight members of the pyrochlore systems (YxLu1−x2V2O7 and (ScxLu1−x)2V2O7 are reported. Critical temperatures are determined for Lu2V2O7 (72.5K) and the other phases to about ± 1K. Trends in Tc, πc, Cm, μeff, and to a lesser extent, μSAT., occur which can be correlated, qualitatively, with thermogravometric data. From (Y.40Lu.60) to (Sc.20Lu.80) the quantities mentioned are nearly constant and analysis indicates the presence of V4+ only. Cm (0.47 cm3K/mole) and μeff (1.94 μB) are significantly greater than the spin-only values of 0.36 and 1.73 respectively. From (Sc.30Lu.70) to (Sc.50Lu.50) a reduced form of vanadium is detected, probably V3+, which increases with Sc content. This is accompanied by a sharp decline in Tc and πc and a sharp increase in Cm and μeff.