Giant magnetic Grüneisen parameters in nearly ferromagnetic and heavy-fermion systems

Abstract

The size of the volume magnetostriction in paramagnetic systems determines a magnetic Gr\uneisen parameter in analogy to the usual thermal Gr\uneisen parameter. Both nearly ferromagnetic and heavy-fermion systems show magnetic Gr\uneisen parameters up to 2 orders of magnitude larger than for normal metals. The thermal Gr\uneisen parameter in nearly magnetic systems, however, remains only modestly enhanced, in strong contrast to heavy-fermion and mixed-valence compounds in which the two Gr\uneisen parameters appear to be of comparable size. The origin of the discrepancy can be understood in terms of the Fermi-liquid parameter ${F}_{0}^{a}$.