Anisotropic manifestation of short-range magnetic correlations in Ce0.6La0.4RhIn5

We report thermal-expansion and magnetostriction results on Ce0.6La0.4RhIn5 single crystals. This particular La concentration (xc∼0.4) corresponds to the critical one at which the long-range magnetic order vanishes (TN=0). However, as also observed in specific heat and magnetic susceptibility measurements, a large “hump” is seen in thermal-expansion at TSR∼4.5K. This anomaly, claimed to be related to short-range correlations, is observed only along the c axis, confirming that anisotropy plays an important role in these 115 compounds. No particular feature is associated with the magnetic correlations in the magnetostriction measurements. The magnetic field dependence of the volume is quadratic in field as expected for a paramagnetic system, above and below TSR. Finally, the magnetic field dependence of the crystal electric field contribution to the thermal expansion seems to reinforce the idea that the La doping leads to a |±5/2⟩-rich ground state doublet