Magnetic Soft Mode Behavior of the Field-Dependent Specific Heat of SrIrO$_{3}$

Previous work\footnote{Cao et al., Phys. Rev. B \textbf{76}, 100402(R),(2007)} indicates SrIrO$_{3}$ is a strongly exchange-enhanced paramagnet (Wilson ratio = 75) exhibiting non-Fermi liquid (NFL) behavior at low magnetic fields, and a cross-over to weak ferromagnetism (0.025 $\mu _{B}$/Ir at $\mu _{o}$H = 7.0 T and T = 1.7 K) at applied fields $\mu _{o}$H $\approx $ 3 T and temperatures T $<$ 4 K. Measurements of the specific heat performed in constant field for 1.8 $<$ T $<$ 4K have been used to extract the field dependence C$_{P}$(H,T$_{o})$(constant T$_{o})$, which exhibits a Schottky-like peak as a function field in the range 1.0 $< \quad \mu _{o}$H $<$ 1.5 T at increasing temperatures 1.8 $<$ T$_{o} \quad <$ 3.9 K, respectively. Fits of C$_{P}$(H,T$_{o})$ imply a nonmagnetic ground state is separated from magnetic excited states by an energy splitting $\Delta $(H,T)/k$_{B}$ = T* that decreases from 7.5 to 2 K as $\mu _{o}$H increases from 0 to 8 T. The Schottky peak field increases as $\mu _{o}$H* = 0.94 T + (0.03 T/K$^{3})$T$^{3.1}$. We discuss how a semi-classical two-level model reproduces the NFL-weak ferromagnet cross-over with applied field.