Structural with Rietveld analysis and enhancement of magnetic, magnetocaloric study of Al substituted Ni–Cd bulk spinel ferrites

Abstract

Ni_0.65Cd_0.35Fe_2-xAl_xO₄ (0 ≤ x ≤ 0.060) disc shape bulk specimen fabricated from the sol–gel synthesized nanocrystalline powders. According to a structural analysis using XRD and Rietveld refinement, single-phase cubic spinel structure confirmed. Crystalline size (40–36) nm calculated using Scherer’s formula. SEM images used to study surface morphology and grain size found decreasing trend from (1.4–1.0) μm. The saturation magnetization (M_s) as well as magnetic moment increased for x = 0.45 and beyond that it decreased with Al content, which phenomenon is attributed due to the reduction of length between tetrahedral (A) sites and octahedral [B] sites of cations. The temperature-dependent magnetization graphs shown sharply declining value of the temperature (i.e., dM/dT maximum) dropping from 582.27 to 578.76 K at the Curie point with Al concentration. The maximum magnetic entropy change (− \(\Delta S_{M}^{\max }\) ) derived from the Maxwell relation, is determined to be (0.54–0.72) JKg⁻¹ K⁻¹ as well as to relative cooling power of (43.18–56.97) Jkg⁻¹ with an applied magnetic field of μ₀H = 3 T. UV–visible spectroscopy utilized to explore optical study and found enhancement of absorption properties with Al content.