Tuning the Spontaneous Exchange Bias Effect in La1.5Sr0.5CoMnO6 with Sintering Temperature

Here, we present a study of the influence of microstructure on the magneticproperties of polycrystalline samples of the La1.5Sr0.5CoMnO6 doubleperovskite, with primary attention to the spontaneous exchange bias effect, afascinating recently discovered phenomena for which some materials exhibitunidirectional magnetic anisotropy after being cooled in zero magnetic fields.By sintering La1.5Sr0.5CoMnO6 at different temperatures, we obtained sampleswith distinct average grain sizes, ranging from 1.54 to 6.65 mu_m. A detailedinvestigation of the material's structural, morphologic, electronic, andmagnetic properties using X-ray powder diffraction, powder neutron diffraction,X-ray absorption near edge structure spectroscopy, scanning electronmicroscopy, and AC and DC magnetometry has revealed a systematic enhancement ofthe exchange bias effect with increasing the average grain size. This evolutionis discussed in terms of changes in the material's porosity and grainmorphology and its influence on the exchange couplings at the magneticinterfaces.