| dc.description |
We describe magnetization measurements on the heavy rare earth titanate pyrochlores R<sub>2</sub> Ti<sub>2</sub> O<sub>7</sub> , where R = Gd, Dy, Ho, Er, Yb, in the temperature range 1.8-300 K, and the field range 0-70 000 Oe. In these materials magnetism arises from the rare earth ions, while Ti is non-magnetic. Analysis of the low field susceptibility versus temperature curves shows that Gd<sub>2</sub> Ti<sub>2</sub> O<sub>7</sub> has antiferromagnetic coupling ( -9 K), which suggests that it is an example of a frustrated antiferromagnet on the pyrochlore lattice. Er<sub>2</sub> Ti<sub>2</sub> O<sub>7</sub> is likewise found to have a large negative Curie-Weiss temperature, -22 K, which we argue is indicative of antiferromagnetic coupling. Ho<sub>2</sub> Ti<sub>2</sub> O<sub>7</sub> , Dy<sub>2</sub> Ti<sub>2</sub> O<sub>7</sub> and Yb<sub>2</sub> Ti<sub>2</sub> O<sub>7</sub> are found to have weak ferromagnetic coupling ( 2 K, 1 K and 1 K respectively) which may be largely dipolar in origin. Fitting of the high field magnetization versus field curves suggests a strong 1,1,1 single ion anisotropy that identifies these three materials as possible realizations of the ferromagnetic `spin ice' model. |
