Magneto-calorimetric studies of reversible magnetisation

Working on well-annealed single-grain samples of YBa2Cu3<f>O7−δ</f> containing 30 mol% of Y2BaCuO5 grown by the seeded melt-growth process, we have obtained values of the field dependence of the free energy, <f>ΔF(Ha,T)</f>, and the reversible magnetisation, <f>Mrev(T)=−(∂ΔF/∂Ha)T</f>, through measurements of the electronic specific heat coefficient <f>γ(Ha,T)</f> in a series of fixed applied magnetic fields <f>Ha</f>. The ability to deduce reliable values of <f>Mrev(0)</f> in the irreversible region of a superconductor is an exciting development as hitherto this quantity could only be poorly estimated from magnetic hysteresis data. [Copyright &y& Elsevier]