The magnetically ordered ground state of CeRhIn$_{ 5}$ at ambient pressure and zero magnetic field is an incomensurate helicoidal phase with the propagation vector $\bf{ k}$=(1/2, 1/2, 0.298) and the magnetic moment in the basal plane of the tetragonal structure. We determined by neutron diffraction the two different magnetically ordered phases of CeRhIn$_{ 5}$ evidenced by bulk measurements under applied magnetic field in its basal plane. The low temperature high magnetic phase corresponds to a sine-wave structure of the magnetization being commensurate with $\bf{ k}$=(1/2, 1/2, 1/4). At high temperature, the phase is incommensurate with $\bf{ k}$=(1/2, 1/2, 0.298) and a possible small ellipticity. The propagation vector of this phase is the same as the one of the zero-field structure.
Categories: cond-mat.str-el