Magnetic and structural properties of pure and Cr-doped haematite: α-Fe2−xCr x O3 (0 ≤ x ≤ 1)

Solid-state ceramic technique route is used for synthesizing Cr-doped haematite α-Fe2−xCr x O3 (x = 0, 0.125, 0.50 and 1) samples. Single phase and corundum (Al2O3) type structure is revealed from the X-ray diffraction (XRD) patterns. The Raman spectra of α-Fe2−xCr x O3 illustrate seven phonon modes. On substitution of Cr (x = 0, 0.125, 0.50 and 1) at Fe site, all Raman active modes are shifted to higher wave numbers. The coercivity and remanence of Cr-doped haematites increase as x increases. The increased coercivity and remanence for Cr-doped samples can be attributed to their enhanced shape and magneto-crystalline anisotropy. The observed isomer shift δ values from room-temperature Mossbauer data clearly show the presence of ferric (Fe3+) and Cr3+ ions illustrating strong ferromagnetic ordering up to x = 0.125 in α-Fe2−xCr x O3 haematite and weak ferromagnetic ordering for α-Fe2−xCr x O3 (x > 0.125) haematites.