Influence of A-site cation disorder on structural and magnetocaloric properties of Nd_0.7–xLa_xSr_0.3MnO₃（x=0.0, 0.1, 0.2 & 0.3）

Sudharshan Vadnala，Prem Pal，Saket Asthana

Department of Physics, Indian Institute of Technology Hyderabad

摘 要：In the present research, the influence of A-site ionic size disorder on structural, magnetic and magnetocaloric properties of Nd0.7–xLaxSr0.3MnO3（for x=0.0, 0.1, 0.2 & 0.3） compounds were investigated. These compounds were synthesized by solid state reaction route and crystallized in orthorhombic structure with Pnma space group. An average ionic radius <r A> increased with La-substitution which influenced the physical properties such as the magnetic entropy varying from 4.78 J/kg·K（for x=0.0） to 3.55 J/kg·K（for x=0.3） and the maximum magnetization at 5 K changing from 3.92 μB（for x=0.0） to 3.59 μB（for x=0.3）. The change in maximum magnetic entropy decreased with increase of A-site average ionic radius. The decrease in magnetic entropy indicated the suppression of lattice disorder that influenced the spin-lattice coupling. The ferromagnetic transition temperature shifted toward room temperature with La substitution. As <r A> increased, the phase transition changed from first order（for x=0.0） to second order（for x≥ 0.1） and the refrigeration capacity increased to a significant level. The modest change in magnetic entropy over a wide range of transition temperature might be useful for future active magnetic refrigeration technology.

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