Dimensionality and irreversibility of field-induced transitions in SrDy2 O4

Low-temperature ultrasound velocity measurements are presented on the frustrated spin system SrDy2O4 that allow us to define high-resolution phase diagrams with the magnetic field applied along all three principal axes. For Hb, a region of field-induced long-range order is delimited by a dome of first-order phase transitions. An unusual magnetization process is observed with significant irreversibility at very low temperatures when passing between the low-field spin liquid phase and the long-range ordered phase which we attribute to large energy barriers. For Hc, the system appears to remain effectively one dimensional, exhibiting two transitions as a function of magnetic field, but no finite-temperature long-range order.