Electronic and Magnetic Properties of Ti1-xMxO2-δ(M=Co and Fe) Thin Films Grown by Sol-gel Method

Abstract

Electronic and magnetic properties of <TEX>$Ti_{1-x}M_xO_{2-\delta}$</TEX> (M=Co and Fe) thin films grown by sol-gel method have been investigated. Anatase and rutile <TEX>$Ti_{1-x}Co_xO_{2-\delta}$</TEX> films were successfully grown on <TEX>$Al_2O_3$</TEX> (0001) substrates and exhibited p-type electrical conductivity while the undoped films n-type conductivity. Room temperature vibrating sample magnetometry measurements on the anatase and rutile <TEX>$Ti_{1-x}Co_xO_{2-\delta}$</TEX> films with same x (<TEX>$=4.8 at.{\%}$</TEX>) showed quite similar magnetic hysteresis curves with the saturation magnetic moment of <TEX>$\~4 {\mu}_B$</TEX> per Co ion despite their differences in structural and electronic properties. Such giant magnetic moment is attributable to the unquenched orbital moment of the <TEX>$Co^{2+}$</TEX> ions substituting the octahedral <TEX>$Ti^{4+}$</TEX> sites. Similar ferromagnetic behavior was observed for <TEX>$Ti_{1-x}Fe_xO_{2-\delta}$</TEX> films that are highly resistive compared to the Co doped samples. Saturation magnetic moment was found to decrease for higher x, i.e., <TEX>$\~2$</TEX> and <TEX>$\~1.5 {\mu}_B$</TEX> per Fe ion for x=2.4 and 5.8 at. <TEX>$\%$</TEX>, respectively. Conversion electron <TEX>$M\ddot{o}ssbauer$</TEX> spectroscopy measurements predicted the coexistence of <TEX>$Fe^{2+}$</TEX> and <TEX>$Fe^{3+}$</TEX> ions at the octahedral sites of <TEX>$Ti_{1-x}Fe_xO_{2-\delta}$</TEX>.