Exchange bias and enhanced coercivity in phase separated La0.45Sr0.55MnO3 and Pr0.55(Ca0.65S0.35)

No abstract

Structural phase transition and Néel temperature (TN) enhancement were observed in Cr-substituted Mn3O4 spinels. Structural, magnetic, and dielectric properties of (Mn1−xCrx)3O4 (where x = 0.00, 0.10, 0.20, 0.25, 0.30, 0.40, and 0.50) were investigated. Cr-substitution induces room temperature structural phase transition from tetragonally distorted I41/amd (x = 0.00) to cubic Fd3¯m (x = 0.50). TN is found to increase from 43 K (x = 0.00) to 58 K (x = 0.50) with Cr-substitution. The spin ordering-induced dielectric anomaly near TN ensures that magneto-dielectric coupling persists in the cubic x = 0.50 system. X-ray absorption spectra reveal that Cr exists in a trivalent oxidation state and prefers the octahedral (Oh)-site, replacing Mn3+. Due to a reduction in the Jahn–Teller active Mn3+ cation and an increase in the smaller Cr3+ cation, the system begins to release the geometrical frustration by lowering its degeneracy. Consequently, a phase transition, from distorted tetragonal structure to the more symmetric cubic phase, occurs.

The traditional magneto-optical Kerr effect (MOKE) measurements involve measuring the intensity of a light reflected off the samples subjected to a DC magnetic field. By superimposing an AC field to the sweeping DC field, and measuring the AC component of the light intensity, we achieved a high signal-to-noise ratio and a better resolution in determining the Curie temperatures of magnetic samples. For a demonstration, we have determined the Curie temperature of a 350 nm thick YIG (yttrium iron garnet, Y 3 Fe 5 O 12 ) thin film to be 511.0 +/− 0.5 K using this method.