Magnetic and electrical transport properties of La_0.87Mn_1−<i>x</i>Fe_<i>x</i>O₃(0 ⩽<i>x</i>⩽ 0.15): coexistence of ferromagnetic and glassy magnetic states

Abstract

We report on the effect of Fe substitution in the self doped manganite, La0.87Mn1−xFexO3 in the composition range 0 ⩽ x ⩽ 0.15. The electrical resistivity (ρ) and dc magnetization were measured as a function of temperature, field and time. The metal to semiconducting transition is clearly observed for x ⩽ 0.02, while a semiconducting temperature dependence of resistivity is noticed for x ⩾ 0.08. The compound with x = 0.05 shows interesting features of ρ in field-cooled (FC) condition such as bifurcation in the zero-field cooled and FC temperature dependence, weak thermal hysteresis and memory effect. We observe the enhancement of colossal magnetoresistance by the Fe substitution in the low substitution range. The paramagnetic to ferromagnetic transition (Tc) is found to decrease with increasing x. The large thermal hysteresis in magnetization under FC condition is noticed for x ⩽ 0.02, which is different in character for the composition range 0.05 ⩽ x ⩽ 0.15. The relaxation of magnetization indicates the ferromagnetic (FM) character for x = 0, while the coexistence of FM and glassy components is observed for x ⩾ 0.02. The glassy magnetic phase increases with the increase in Fe substitution. The inhomogeneous phase separation between FM and glassy magnetic phases has been proposed to explain the magnetic and electrical transport properties of La0.87Mn1−xFexO3.