Investigation of structural transport and magnetic properties of the system Li_0.25Cu_0.5Fe_2.25- _x Al _x O₄

Abstract

Experimental data on X-ray electrical conductivity, thermoelectric coefficient, magnetic hysteresis and infrared absorption spectra of the system Li_0.25Cu_0.5Fe_2.25−x Al _x O₄ are presented. All the compounds, 0⩽x⩽2.25, showed cubic symmetry. Lattice constant values progressively decreased on increasing the Al³⁺ content. X-ray intensity calculations, magnetic hysteresis and infrared spectroscopy studies indicated the presence of Li⁺, Al³⁺ and Fe³⁺ at tetrahedral and octahedral sites, while Cu²⁺ is present only at the octahedral site. The activation energy and threshold frequency increased with increasing values ofx. The compounds withx⩽1.50 aren-type, and those withx⩾2.0 arep-type semiconductors. Magnetic hysteresis indicated that compounds withx⩽1.50 are ferrimagnetic, and those withx⩾2.0 are antiferrimagnetic. High coercive force,H _c, values and remanence ratios (J _R/J_S) showed that all the compounds exceptx⩾2.0 exhibit single-domain behaviour. The probable ionic configuration for the system is suggested as Li ⁺_0.15 Al ³⁺_0.5 Fe ³⁺_0.35 [Li ⁺_0.1 Cu ²⁺_0.5 Fe ³⁺_0.4 Al³⁺]O ²⁻₄ .