The critical magnetic fields required to induce the magnetostructural transformation below $\sim 30\mathrm{K}$ in ${\mathrm{Gd}}_5{\mathrm{Ge}}_4$ are dependent on the size of the magnetic-field step employed during isothermal measurements of magnetization: the smaller the step, the lower the critical field. The influence of the magnetic-field step size on the character of the magnetostructural transition in ${\mathrm{Gd}}_5{\mathrm{Ge}}_4$ diminishes as temperature increases, nearly disappearing above $\sim 30\mathrm{K}$. Decreasing the size of the field step also leads to the formation of multiple steps in the magnetization. The steps are reproducible in the same sample at low temperatures (below $\sim 9\mathrm{K}$) but they become stochastic and irreproducible at high temperatures (above $\sim 20\mathrm{K}$). The varying dynamics of both the magnetization and demagnetization processes is associated with approaching true equilibrium states and, therefore, reduction of the size of the magnetic-field step at low temperatures plays a role similar to the dominant role of thermal fluctuations at high temperatures. Similar phenomena are expected to occur in other martensiticlike systems, e.g., the manganites.

• Received 29 June 2007

DOI:https://doi.org/10.1103/PhysRevB.76.134406