Magnetic structure of rare-earth dodecaborides

We have investigated the magnetic structure of HoB12, ErB12 and TmB12 by neutron diffraction on isotopically enriched single-crystalline samples. Results in zero field as well as in magnetic field up to 5 T reveal modulated incommensurate magnetic structures in these compounds. The basic reflections can be indexed with q=(1/2±δ, 1/2±δ, 1/2±δ), where image both for HoB12 and TmB12 and with q=(3/2±δ, 1/2±δ, 1/2±δ), where image, for ErB12. In an applied magnetic field, new phases are observed. The complex magnetic structure of these materials seems to result from the interplay between the RKKY and dipole–dipole interaction. The role of frustration due to the fcc symmetry of dodecaborides and the crystalline electric field effect is also considered.