Elastic and magnetic properties of the bilayer manganese oxide(Pr0.6La0.4)1.2Sr1.8Mn2O7

Abstract

The elastic and magnetic properties of a single crystal of the bilayer manganese oxide ${({\mathrm{Pr}}_{0.6}{\mathrm{La}}_{0.4})}_{1.2}{\mathrm{Sr}}_{1.8}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ have been investigated by means of ultrasonic and high-field magnetization measurements. Remarkable changes in the elastic constants ${C}_{11}$, ${C}_{33}$, ${C}_{44}$, and ${C}_{66}$ as a function of temperature and magnetic field have been observed. In particular, a distinct elastic anomaly was observed at low temperatures and in magnetic fields when crossing the phase boundary between the paramagnetic insulating and the field-induced ferromagnetic metallic state. A pronounced elastic softening as a function of magnetic field $(H)$ appears across the boundary of the low-temperature magnetic phase below around $40\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, accompanied by a distinct hysteresis. In the high-field region, however, these elastic constants exhibit a monotonic increase upon increasing the magnetic field. The high-field magnetization measurements characterizing the magnetic state point out a strong coupling between the elastic strain and the magnetic moment. The data can be described reasonably well considering a strong coupling between elastic strain and magnetic susceptibility ${\ensuremath{\chi}}_{m}=\ensuremath{\partial}M∕\ensuremath{\partial}H$.