Despite its significance for applications, fundamental magnetic properties of Gd are still under debate including the very nature of its magnetic ordering . We explore unusual properties of Gd including the absence of hysteresis in magnetization isotherms below TC=292 K. We employ magnetometry, heat capacity, and magnetic force microscopy to show that the magnetic behavior in applied magnetic fields, Ha, is richer than its idealized descriptions in terms of internal magnetic fields. In an experimental situation, the isothermal first order transition takes place via quasi-equilibrium multi-domain states giving rise to a non-zero isothermal entropy change ΔS=S(Ha,T)-S(0,T). We show that under certain conditions the Maxwell relation is valid also for Ha and apply it to determine ΔS at 280 K≤T≤TC. For small magnetic fields, ΔS is virtually temperature independent giving rise to a constant isothermal heat capacity.
 J. M. D. Coey, V. Skumryev, K. Gallagher, Nature, 401, 35, (1999)