Magnetic phase diagrams of Y-diluted antiferromagnet Tb1-xYxB2C2 (0.2≤x≤0.5)

Magnetic B-T phase diagrams were examined by magnetization and specific heat experiments on the single crystalline Tb1-xYxB2C2 (0.2≤x≤0.5) compounds, and neutron diffraction experiments was performed on the powder Tb0.5Y0.511B2C2 sample. The magnetization curves evidence that the field-induced transition occurs from phase IV into phase II' through a mixed phase of both phases, where phase IV is antiferromagnetic and phase II' is a field-induced phase with the antiferromagnetic and antiferroquadrupolar order. The mixed phase (IV + II') is enhanced by the Y-dilution, and the lower and upper verges of the mixed phase become clearer in the differential magnetization dM/dB-B curves. The Y-dilution results in scaling down of the ordered phases regions in the B-T space. The ways of scale down of the ordered phase are different between two field directions along the tetragonal [100] and [110]-axes, that is, the anisotropy of phase stability is increased by the Y dilution. It is supposed that the enhancement of anisotropic phase stability by the Y dilution may be due to the symmetry of the multipoles and the anisotropic multipolar interactions weakended by the Y dilution. (author)