Structural, magnetic and magnetotransport properties of the La0.67Ca0.33Mn0.9Fe0.1O3 perovskite

Magnetization, AC susceptibility, Mossbauer spectroscopy, neutron diffraction (ND) and magneto resistance measurements have been carried out on a polycrystalline perovskite, La0.67Ca0.33Mn0.9Fe0.1O3. 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 Mossbauer spectrum reveals that Fe substitutes for Mn as Fe3+ (S = 5/2) and is antiferromagnetically coupled to the Mn host lattice. The substitution of Mn3+ by Fe3+ reduces the number of available hopping sites for the Mn e,(T) 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 50-80K 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 Fe3+ for Mn3+ drive the system supposedly into a random canted ferromagnetic state at low temperatures. (C) 2003 Elsevier Science B.V. All rights reserved.