title: Determination of the entropy via measurement of the magnetization: application to the spin ice Dy₂Ti₂O₇.
abstract: The residual entropy of spin ice and other frustrated magnets is a property of considerable interest, yet the usual way of determining it, by integrating the heat capacity, is generally ambiguous. Here we note that a straightforward alternative method based on Maxwell's thermodynamic relations can yield the residual entropy on an absolute scale. The method utilizes magnetization measurements only and hence is a useful alternative to calorimetry. We confirm that it works for the spin ice Dy₂Ti₂O₇, which recommends its application to other systems. The analysis described here also gives an insight into the dependence of entropy on magnetic moment, which plays an important role in the theory of magnetic monopoles in spin ice. Finally, we present evidence of a field-induced crossover from correlated spin ice behaviour to ordinary paramagnetic behaviour with increasing applied field, as signalled by a change in the effective Curie constant.
authors.affiliation: London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, 17-19 Gordon Street, London WC1H 0AJ, UK. l.bovo@ucl.ac.uk
authors.forename: L
authors.initials: L
authors.lastname: Bovo
authors.forename: S T
authors.initials: ST
authors.lastname: Bramwell
mesh_terms: D003198:Computer Simulation; D019277:Entropy; D005615:Freezing; D060526:Magnetic Fields; D059346:Magnets; D008956:Models, Chemical; D008958:Models, Molecular; D044367:Phase Transition; D013113:Spin Labels
chemical_list: D013113:Spin Labels