  Recent progress in the fabrication techniques of superlattices (SLs) has made
it possible to sandwich several-layer-thick block layers (BLs) of heavy-fermion
superconductor CeCoIn5 between conventional-metal YbCoIn5 BLs or
spin-density-wave-metal CeRhIn5 BLs of a similar thickness. However, the
magnetic state in each BL, particularly at the interface, is not yet
understood, as experimental techniques applicable to the SL system are limited.
Here, we report measurements of 59Co nuclear magnetic resonance, which is a
microscopic probe of the magnetic properties inside the target BLs. In the
CeCoIn5/YbCoIn5 SL, the low-temperature magnetic fluctuations of the CeCoIn5 BL
are weakened as expected from the Rashba spin-orbit effect. However, in the
CeCoIn5/CeRhIn5 SL, the fluctuations show an anomalous enhancement below 6 K,
highlighting the importance of the magnetic proximity effect occurring near a
magnetic-ordering temperature TN ~ 3 K of the CeRhIn5 BL. We suggest that the
magnetic properties of the BLs can be altered by the interfacial interaction,
which is an alternative route to modify the magnetic properties.
