Restoration of magnetization reversal under hydrostatic pressure in the lightly electron-doped manganite compound (Ca,Sr)Mn0.95Sb0.05O3

We report on the anomalous magnetization reversal under hydrostatic pressure in the lightly electron-doped manganite compound (Ca$_{1-x}$Sr$_{x}$)Mn$_{0.95}$Sb$_{0.05}$O$_{3}$ with its fixed carrier content. In a weakly magnetic field cooled measurement, diamagnetic magnetization is observed for $x\leq 15\%$, which changes to positive values for $x>15\%$. However, on an application of pressure on the samples with $x=16\%$ and 17$\%$, magnetization reverses sign and diamagnetism is restored. We present a magnetic phase diagram as a function of Sr concentration, under both ambient and hydrostatic pressures. To understand better the thermodynamical properties of this system, we have measured the specific heat as a function of temperature under a field cooling of 100 Oe. Our data show no anomalies associated with the temperature dependent magnetization reversal, indicating the absence of a long-rang magnetic ordering. The $ac$ magnetic susceptibility measurement points to the existence of magnetic frustration for the Sr substituted samples exhibiting diamagnetic behavior.