An adiabatic demagnetization process is studied in Gd2Ti2O7, a geometrically frustrated antiferromagnet on a pyrochlore lattice. In contrast to conventional paramagnetic salts, this compound can exhibit a temperature decrease by a factor of ten in the temperature range below the Curie-Weiss constant. The most efficient cooling is observed in the field interval between 120 and 60 kOe corresponding to a crossover between saturated and spin-liquid phases. This phenomenon indicates that a considerable part of the magnetic entropy survives in the strongly correlated state. According to the theoretical model, this entropy is associated with a macroscopic number of local modes remaining gapless till the saturation field. Monte Carlo simulations on a classical spin model demonstrate good agreement with the experiment. The cooling power of the process is experimentally estimated with a view to possible technical applications. The results for Gd2Ti2O7 are compared to those for Gd3Ga5O12, a well-known material for low temperature magnetic refrigeration.
@article{arxiv.cond-mat/0404529,
title = {Magnetocaloric effect in pyrochlore antiferromagnet Gd2Ti2O7},
author = {S. S. Sosin and L. A. Prozorova and A. I. Smirnov and A. I. Golov and I. B. Berkutov and O. A. Petrenko and G. Balakrishnan and M. E. Zhitomirsky},
journal= {arXiv preprint arXiv:cond-mat/0404529},
year = {2007}
}