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

Magnetization, AC susceptibility, Mössbauer spectroscopy, neutron diffraction (ND) and magnetoresistance 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 Mössbauer 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 eg(↑) electron and suppresses the double exchange (DE), resulting in the reduction of ferromagnetic exchange as evidenced by a decrease of about 125K in the value of ferromagnetic ordering temperature (TC) and of about 183K in the value of metal-to-insulator transition temperature (Tp) without Fe. This compound presents 98% of giant magnetoresistance ratio in the temperature range of 50–80K at 40kOe 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.