Dimensionality and irreversibility of field-induced transitions in SrDy 2 O 4

In this work, the ultrasound velocity is measured in the frustrated spin liquid material SrDy${}_{2}$O${}_{4}$ as a function of magnetic field and temperature. Experimental data reveals a complex phase diagram that depends heavily on the direction of the magnetic field. Whereas a dome for the three-dimensional long-range magnetic order is induced for magnetic field applied along the $b$ axis, no finite temperature magnetic order is observed for other field directions. When passing between the spin liquid and magnetically ordered phase, significant irreversibility is observed. ``Solidification'' of the spin liquid (through applied field) proceeds through three distinct steps while melting of the magnetic order into the spin-liquid phase is a more continuous process.