Coexisting Magnetic Order and Cooperative Paramagnetism in the Stuffed Pyrochlore Tb2+xTi2-2xNbxO7

 

Benjamin G. Ueland, J.S. Gardner, A.J. Williams, M.L. Dahlberg, J.G. Kim, Y. Qiu, J.R.D. Copley, P. Schiffer, and R. J. Cava

 

            Neutron scattering and magnetization measurements have been performed on the stuffed pyrochlore system Tb2+xTi2-2xNbxO7.  We find that despite the introduction of chemical disorder and increasingly antiferromagnetic interactions, a spin glass transition does not occur for T ≥ 1.5 K and cooperative paramagnetic behavior exists for all x.  For x = 1, Tb3NbO7, an antiferromagnetically ordered state coexisting with cooperative paramagnetic behavior is seen without applying any external fields or pressure, a situation advantageous for studying this cooperative behavior.