  The effect of hydrostatic pressure on the incommensurate antiferromagnetic
structure of CeRhIn5 is investigated with neutron diffraction using a He
pressure cell. At 3.8 kbar, the staggered magnetic moment is 0.37(4) Bohr
magneton per Ce at 1.6 K, which is the same as the ambient-pressure value. The
Neel temperature T_N=3.8(1) K is also the same as the ambient-pressure one,
although the curve of order parameter has changed by pressure. The
incommensurability "delta" of the magnetic wave vector q_M=(1/2,1/2,"delta")
has reduced from "delta"=0.297 at ambient pressure to "delta"=0.294(1) at 3.8
kbar.
