Structural, magnetic and magnetotransport properties of the La 0.67Ca 0.33Mn 0.9Fe 0.1O 3 perovskite

Abstract

Magnetization, AC susceptibility, Mössbauer spectroscopy, neutron diffraction (ND) and magnetoresistance measurements have been carried out on a polycrystalline perovskite, La 0.67Ca 0.33Mn 0.9Fe 0.1O 3. Considerable changes occur in magnetic, transport and magnetoresistance properties with respect to the classic composition without Fe but no spin-glass like behavior is observed. ND data confirms that the compound crystallizes in the orthorhombic perovskite structure (space group Pbnm). The Mössbauer spectrum reveals that Fe substitutes for Mn as Fe 3+ ( S=5/2) and is antiferromagnetically coupled to the Mn host lattice. The substitution of Mn 3+ by Fe 3+ reduces the number of available hopping sites for the Mn e g(↑) electron and suppresses the double exchange (DE), resulting in the reduction of ferromagnetic exchange as evidenced by a decrease of about 125 K in the value of ferromagnetic ordering temperature ( T C) and of about 183 K in the value of metal-to-insulator transition temperature ( T p) without Fe. This compound presents 98% of giant magnetoresistance ratio in the temperature range of 50–80 K at 40 kOe applied magnetic field. The competition between the ferromagnetic DE interactions and the coexisting anti-ferromagnetic super exchange interactions with the introduction of Fe 3+ for Mn 3+ drive the system supposedly into a random canted ferromagnetic state at low temperatures.