Neutron scattering and a.c. susceptibility studies on the geometrically frustrated Tb2Ti2O7

We have performed neutron scattering and a.c. susceptibility chi (a.c). stu dies on polycrystallline Tb2Ti2O7 to investigate the magnetic correlations in this antiferromagnetic pyrochlores. Evidence of changes in the magnetic correlation length has been observed by neutron diffraction in different pa rts of an applied field/temperature phase diagram. This cooperative paramag net has been shown to increase its magnetic correlations, from nearest neig hbour to similar to 100 Angstrom, in modest fields (<7 T) and temperatures (T > 2 K); however, in zero field the system does not order above 15 mK, ev en with its large moment.