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

The tuning effects of Al3+ doping on the magnetic and magnetotransport properties of La 0·6 Ca 0·4 MnO 3- δ have been studied by preparing series La 0·6 Ca 0·4 Mn 1- x Al x O 3- δ (x = 0, 0.1, 0.125 and 0.15). Al3+ doping suppresses the ferromagnetic metal phase of La 0·6 Ca 0·4 MnO 3- 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 = 0.125 and 0.15 system below 4.2 K. Phase diagrams of La 0·6 Ca 0·4 Mn 1- x Al x O 3- δ (0.1 ≤ x ≤ 0.15) 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. • Phase separation scenario is induced by Al3+ doping in La 0·6 Ca 0·4 Mn 1- x Al x O 3- δ. • Martensitic-like transition was observed in x = 0.125 and 0.15 systems below 4.2 K. • The pinning effects of disorder play a crucial role in martensitic-like transition. • Phase diagram of La 0·6 Ca 0·4 Mn 1- x Al x O 3- δ (0.1 ≤ x ≤ 0.15) in B - T plane is obtained. [ABSTRACT FROM AUTHOR]