Orbital order-disorder transition in doped perovskite manganites: influence of intrinsic octahedral-site distortion

TL;DR

This study investigates how doping levels and intrinsic octahedral-site distortions influence the orbital order-disorder transition in doped perovskite manganites, revealing a doping-dependent maximum in transition temperature related to structural distortions.

Contribution

It uncovers the doping-dependent behavior of the transition temperature and distortion, highlighting the influence of charge carriers on intrinsic structural biases in manganites.

Findings

Transition temperature T_OO shows non-monotonic behavior beyond 10% doping.

Maximum T_OO occurs at a doping-dependent critical tolerance factor t_C.

Intrinsic octahedral-site distortion influences the orbital order in doped manganites.

Abstract

The orbital order-disorder transition temperature (T_OO) versus tolerance factor (t) plot switches from monotonic to non-monotonic beyond a doping level (x) ~ 10 atom% in a family of R(1-x)A(x)MnO3 systems(R = La, Pr, Nd; A = Ca, Sr; x = 0.0-0.2). T_OO reaches maximum at a 'doping-dependent' critical tolerance factor t_C(x) (for 0.1<x<0.2)at which the orthorhombic distortion (D) also maximizes. Such an observation reflects influence of charge carriers on both 'intrinsic' octahedral-site distortion and its bias on the orbital order in doped perovskite manganites and, thus, deviation from what has been observed in undoped RMnO3, RTiO3, and RVO3 systems where maximization of T_OO and D takes place at a universal tolerance factor or R-site ion size.