Excess specific heat and evidence of zero-point entropy in magnetic glassy state of half-doped manganites

Abstract

We show that specific heat ${C}_{p}$ has non-Debye behavior for glassy states in half-doped manganites. Irrespective of the magnetic order or electronic states, these magnetic glasses have higher ${C}_{p}$ compared to their equilibrium counterparts. The excess ${C}_{p}$ contributed by the glassy state varies linearly with temperature similar to conventional glasses indicating tunneling in the two-level systems. These glassy states show signature of zero-point entropy. Magnetic glasses can be produced simply by different field cooling protocols and may be considered ideal magnetic counterpart of the conventional glass.