Magnetisation Studies of Geometrically Frustrated Antiferromagnets SrLn2O4, with Ln = Er, Dy and Ho

We present the results of susceptibility \chi(T) and magnetisation M(H) measurements performed on single crystal samples of the rare-earth oxides SrLn2O4 (Ln = Er, Dy and Ho). The measurements reveal the presence of magnetic ordering transition in SrHo2O4 at 0.62 K and confirm that SrEr2O4 orders magnetically at 0.73 K, while in SrDy2O4 such a transition is absent down to at least 0.5 K. The observed ordering temperatures are significantly lower than the Curie-Weiss temperatures, \theta_{CW}, obtained from the high-temperature linear fits to the 1/\chi(T) curves, which implies that these materials are subject to geometric frustration. Strong anisotropy found in the \chi(T) curves for a field applied along the different crystallographic directions is also evident in the M(H) curves measured both above and below the ordering temperatures. For all three compounds the magnetisation plateaux at approximately one third of the magnetisation saturation values can be seen for certain directions of applied field, which is indicative of field-induced stabilisation of a collinear {\it two-up one-down} structure.