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and are members of the Aurivillius family of compounds having simultaneous electrical and magnetic ordering. Magnetoelectric measurements carried out in a linear time-varying magnetic field with an alternating-current field superimposed yielded a non-linear signal. The shift from linearity, which is not usually observed for antiferromagnetic materials, may be due the tilt in the octahedra. The variation of the magnetoelectric output with temperature for and indicated magnetic anomalies with enhanced sensitivity, corresponding to those in magnetization data.

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Co and Mn doped ZnO nanocrystals have been synthesized by two different routes, viz., a wet chemical method and a microwave-assisted nonaqueous method and it has been found that the samples prepared by the former method are ferromagnetic while those prepared through the later route are paramagnetic. Systematic investigation of these doped ZnO nanocrystals has been carried out by extended X-ray absorption fine structure technique to determine the changes in the local structure at the Zn and dopant sites. Co doped samples prepared by either of the techniques show almost similar behavior, with Co substituting Zn up to a 10% doping concentration, beyond which there is a signature of Co clustering. However, in the case of Mn doped samples, Mn clustering commences at lower values of doping (∼7%) for samples prepared by microwave-assisted method, while for nanocrystals prepared by the wet chemical method, Mn−K edge X-ray absorption near edge spectroscopy measurement reveals the presence of a Mn 2 O 3 phase at lower concentration and clustering at higher concentration (>10%). These findings were supported by the results of optical and magnetic measurements on the samples. The experimental results have been further corroborated by first principle calculations. The findings suggest that the origin of ferromagnetic properties in Co doped ZnO nanoparticles prepared by the wet chemical method may be a consequence of surface modification related to the preparation process and not related to bulk properties. The ferromagnetism in Mn doped samples prepared by the wet chemical method can be explained by the presence of a secondary Mn 2 O 3 phase. The Mn doped samples prepared by the microwave-assisted method, on the other hand, manifest paramagnetism with a signature of antiferromagnetic interaction due to Mn clustering at relatively lower Mn concentration.

BiFeO3 forms solid solutions with BaTiO3, over the entire compositional range, with different crystal symmetries. Magnetoelectric (ME) measurements carried out with a superimposed alternating-current magnetic field, together with a time-varying direct-current magnetic field in isothermal conditions, indicated non-linearity. The peak observed coincided with a metamagnetic transition in the magnetization data. Rather than the spin flop reported earlier, it is a gradual reorientation of spins towards the field direction that destroys the spiral spin arrangement. With increasing content of BaTiO3, a quadratic signal was observed, indicating the structural dependence of the magnetoelectric effect. The temperature variation of the ME output in the investigation carried out for x = 0.75 indicates magnetic transitions.