  Muon spin relaxation on Nd$_2$Ti$_2$O$_7$ (NTO) and NdLaTi$_2$O$_7$ (NLTO)
compounds are presented. The time spectra for both compounds are as expected
for the paramagnetic state at high temperatures, but deviate from the
exponential function below about 100 K. The muon spin relaxation rate increases
with decreasing temperature firstly, and then levels off below about 10 K,
which is reminiscent of the frustrated systems. An enhancement of the
relaxation rate by a longitudinal field in the paramagnetic state is observed
for NTO, and eliminated by a magnetic dilution for the NLTO sample. This
suggests that the spectral density is modified by a magnetic dilution and thus
indicates that the spins behave cooperatively rather than individually.
Zero-field measurement at 0.3 K indicates that the magnetic ground state for
NTO is ferromagnetic.
