The doping and temperature dependences of the Hall coefficient, R(H), and ab-plane resistivity in the normal state down to 350 mK is reported for oriented films of the electron-doped high-T(c) superconductor Pr(2-x)Ce(x)CuO(4-delta). The doping dependences of beta (rho=rho(0)+ATbeta) and R(H) (at 350 mK) suggest a quantum phase transition at a critical doping near x=0.165.

Occurrence of room temperature ferromagnetism is demonstrated in pulsed laser deposited thin films of Sn 1-x Co x O 2-δ (x<0.3). Interestingly, films of Sn 0.95 Co 0.05 O 2-δ grown on R-plane sapphire not only exhibit ferromagnetism with a Curie temperature close to 650 K, but also a giant magnetic moment of 7 ± 0.5 µ B /Co, not yet reported in any diluted magnetic semiconductor system. The films are semiconducting and optically highly transparent.

We report a detailed magnetic and structural analysis of highly reduced Co doped rutile TiO 2-δ films displaying an anomalous Hall effect (AHE). The temperature and field dependence of magnetization, and transmission electron microscopy clearly establish the presence of nano-sized superparamagnetic cobalt clusters of ~8-10 nm size in the films at the interface. The co-occurrence of superparamagnetism and AHE raises questions regarding the use of the AHE as a test of the intrinsic nature of ferromagnetism in diluted magnetic semiconductors.

Pulsed laser deposited films of Co doped anatase TiO 2 are examined for Co substitutionality, ferromagnetism, transport, magnetotransport and optical properties. Our

Ferromagnetism is observed at and above room temperature in pulsed laser deposited epitaxial films of Co-doped Ti-based oxide perovskite (La 0.5 Sr 0.5 TiO 3-δ ). The system has the characteristics of an intrinsic diluted magnetic semiconductor (metal) at low concentrations (< ~ 2 %), but develops inhomogeneity at higher cobalt concentrations.The films range from being opaque metallic to transparent semiconducting depending on the oxygen pressure during growth and are yet ferromagnetic.