Role of external and internal perturbations on the ferromagnetic phase transition inSm0.52Sr0.48MnO3

Abstract

We report on the magnetic field $(H)$, hydrostatic pressure $(P)$, and doping dependence of the order of the ferromagnetic (FM) to paramagnetic (PM) phase transition in ${\text{Sm}}_{0.52}{\text{Sr}}_{0.48}{\text{MnO}}_{3}$ single crystal. It has been shown that $({H}_{\text{cr}}\ensuremath{\approx}4\text{ }\text{T},\text{ }{T}_{\text{cr}}\ensuremath{\approx}160\text{ }\text{K})$ is a critical point below which FM to PM phase transition is first order in nature accompanied by a sharp drop in resistivity and magnetization with thermal hysteresis. Below the critical point, these parameters also show field-induced metamagnetic transition along with hysteresis between the increasing and decreasing fields. All these signatures of first-order FM transition disappear above the critical point and the transition becomes a crossover. The effect of $P$ on the nature of FM-PM transition is quite similar to that of $H$ and the corresponding critical point, where the character of FM transition that changes from first to second order is $({P}_{\text{cr}}\ensuremath{\approx}2.5\text{ }\text{GPa},\text{ }{T}_{\text{cr}}\ensuremath{\approx}160\text{ }\text{K})$. We have also determined the location of critical point expressed in terms of Nd concentration $(y)$ of ${({\text{Sm}}_{1\ensuremath{-}y}{\text{Nd}}_{y})}_{0.52}{\text{Sr}}_{0.48}{\text{MnO}}_{3}$ and found that the transition changes to second order at $({y}_{\text{cr}}\ensuremath{\approx}0.4,\text{ }{T}_{\text{cr}}\ensuremath{\approx}175\text{ }\text{K})$. The change in the character of FM transition with the application of external ($H$ and $P$) and internal (Nd concentration) perturbations has been explained within the framework of the formation of polarons.