Novel magnetic behavior of single-crystalline Er ₂PdSi ₃

We report the results of ac and dc magnetic susceptibility (χ) and electrical resistivity (ρ) measurements on the single crystals of Er ₂PdSi ₃, crystallizing in an AlB ₂-derived hexagonal structure, for two orientations H//[0 0 0 1] and H//[2110]. For H//[0 0 0 1], there are apparently two magnetic transitions as revealed by the χac data, one close to 7 K attributable to antiferromagnetic ordering and the other around 2 K. However, for H//[2110], we observe additional features above 7 K (near 11 and 23 K) in the plot of low field χ(T); also, there is no corresponding anomaly in the ρ(T) plot. In this respect, the magnetic behavior of this compound is novel, particularly while compared with other members of this series. The features in χac respond differently to the application of a small dc magnetic field for the two directions. As far as low-temperature (T=1.8 and 5 K) isothermal magnetization (M) behavior is concerned, it exhibits metamagnetic-like features around 2 kOe saturating at high fields for the former orientation, whereas for the latter, there is no saturation even at 120 kOe. The sign of paramagnetic Curie temperature is different for these two directions. Thus, there is a strong anisotropy in the magnetic behavior. However, interestingly, the ρ(T) plots are found to be essentially isotropic, with the data revealing possible formation of magnetic superzone formation below 7 K.