Influence of rare-earth doping on the structural and magnetic properties of orthoferrite La0.50R0.50FeO3 ceramics obtained under high pressure

Abstract

Studies on the impact of co-doping on the structural, magnetic, and magnetocaloric properties of LaFeO3 orthoferrite-based compounds with partial isovalent substitution of La3+ by rare-earth (R) ions have been carried out. Their functional properties have been experimentally and theoretically investigated by X-ray diffraction analysis, differential scanning calorimetry, and magnetic methods as well as a semiempirical approach. The La0.50R0.50FeO3 (R = Nd, Eu, Gd, Dy, Er) ceramics have been taken as a basis and prepared by a solid-state reaction method under cold-pressing at high pressure (P = 4 GPa). The temperature dependences of the magnetization and magnetocaloric characteristics of the La0.50R0.50FeO3 orthoferrites for the whole series of substitutions from R = Ce to Lu have been calculated within the framework of the semiempirical model, assuming linearity of its parameters depending on the R cation radius. The magnetic entropy change ΔSM, relative cooling power RCP, and specific heat capacity ΔCP,H have thereby been obtained. It has been shown that the La0.50Ce0.50FeO3 composition has the highest magnetocaloric parameters with the lowest Néel temperature TN. As the R cation radius decreases, the chemical pressure increases, leading to a decrease in the magnetocaloric characteristics and an increase in TN. This is due to both a size effect of the crystallites and structural distortions. The obtained results show the potential practical applications of orthoferrite-based materials with controlled magnetocaloric effect and phase transition temperature.