Tuning of Al doping on martensitic-like transition in phase separated manganites La0.6Ca0.4Mn1-xAlxO3-δ

Abstract

Abstract The tuning effects of Al3+ doping on the magnetic and magnetotransport properties of La0·6Ca0·4MnO3-δ have been studied by preparing series La0·6Ca0·4Mn1-xAlxO3-δ (x\u202f=\u202f0, 0.1, 0.125 and 0.15). Al3+ doping suppresses the ferromagnetic metal phase of La0·6Ca0·4MnO3-δ by weakening the double-exchange interaction of Mn3+-O2--Mn4+, leading to a phase separation state. Al3+ doping dependent irreversible metamagnetic transitions are observed at lower temperatures, especially a martensitic-like transition appears in x\u202f=\u202f0.125 and 0.15 system below 4.2\u202fK. Phase diagrams of La0·6Ca0·4Mn1-xAlxO3-δ (0.1\u202f≤\u202fx\u202f≤\u202f0.15) in the B-T plane are presented, in which the antiferromagnetic insulator and ferromagnetic metal phases boundary is figured out. The antiferromagnetic matrix and magnetic disorders caused by the random distribution of Al3+ ions and the spontaneous oxygen vacancies grow into a pinning center to pin the Mn moments. As magnetic field is increased to the critical field, the localized magnetic moments rotate to parallel to the magnetic field direction, leading to a martensitic-like transition.