Multiferroic composites are promising candidates for magnetic field sensors, next-generation low power memory and spintronic devices, as they exhibit much higher magnetoelectric (ME) coupling and coupled ordering parameters compared to the single-phase multiferroics. Hence, the 3-0 type particulate multiferroic composites having general formula (1 − Φ)[PbFe0.5Nb0.5O3]-Φ[Co0.6Zn0.4Fe1.7Mn0.3O4] (Φ = 0.0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, (1 − Φ) PFN-ΦCZFMO) were prepared using a hybrid synthesis technique. Preliminary structural and microstructural analysis were carried out using XRD and FESEM techniques, which suggest the formation of 3-0 type particulate composite without the presence of any impurity phases. The multiferroic behaviour of the composites is studied with polarization versus electric field (P-E) and magnetization versus magnetic field (M-H) characteristics at room temperature. The nature of ME coupling was investigated elaborately by employing the Landau free energy equation along with the magneto-capacitance measurement. This investigation suggests the existence of biquadratic nature of ME coupling (P2M2). The magneto-electric coupling measurement also suggests that strain mediated domain coupling between the ferroelectric and magnetic ordering is responsible for the magneto-electric behaviour. The obtained value of direct ME coefficient 26.78 mV/cm-Oe for Φ = 0.3, found to be higher than the well-known single-phase materials and polycrystalline composites.

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There is a confocal attention of the multifunctional material science and condensed matter physics research community to the room temperature (RT) magnetoelectric multiferroics through past several decades for its novel physical and chemical properties. Materials with substantial coupling at RT are still an unsaturated problem in the field of condensed matter physics. Apart from searching new magnetoelectrics, enhancement of the coupling as well as physical properties by manipulating the size dependency of these properties also very popular. Here, we report the presence of substantial magnetoelectric cooping in Nanocrystalline Fe 2 TeO 6 (FTO) at room temperature synthesized by sol-gel process. The nano aspect of FTO is confirmed from transmission electron microscopy, where the particles of sizes 10-40 nm are seen. Magnetic measurement on nano-FTO confirms the antiferromagnetic nature of particles having Nѐel temperature T N = 167 K, which is much lower than that of bulk (210 K). PE loop measurement at room temperature gives the remanent polarization (P r) value of 0.098 μC/cm 2 , confirming ferroelectricity in FTO. A nonmonotonous increase in the remanent polarization is noticed when an external magnetic field is applied on the sample. This is a clear indication of prevailing substantial magnetoelectric (ME) coupling in the sample at room temperature. Quantification of magnetoelectricity is done by directly measuring the ME voltage (V) in the presence of varying dc magnetic field (H) and the ME coefficients are obtained using a quadratic relation in H. Presence of ferroelectricity and magnetoelectricity above the Nѐel temperature is very unusual phenomenon in this material. The presence of short range magnetic ordering which prevails even upto RT, much higher that of long range magnetic ordering temperature is suspected to be responsible for this.

We have reported a systematic investigation on structural, magnetic, magnetodielectric and magnetoimpedance characteristics of Y-type Ba 2 Mg 2 (Fe 1−x Mn x ) 12 O 22 (0 ⩽ x ⩽ 0.12) hexaferrite synthesized by solid-state reaction route. Rietveld refinement of x-ray diffraction pattern confirms the phase purity of all the samples with rhombohedral crystal structure. The Mn dopant modulates not only superexchange angle near to the boundary of magnetic blocks but also magnetic transition temperature. Temperature-dependent magnetization data suggests that due to Mn doping at Fe sites, ferrimagnetic to proper screw transition temperature (T II ) increases from 190 K to 208 K, while there is a decrease in proper screw to longitudinal conical spin transition temperature (T I ) from 35 K to 25 K. We observe remarkable decrease in the magnetic field from 20 kOe to 12 kOe to produce intermediate spin ordering from ferrimagnetic ordering which can be understood because of modification of superexchange angle due to Mn doping. The value of loss tangent decreases with increasing doping concentration at 300K, i.e. ~60% and 180% in BMFM4 (x = 0.04) and BMFM8 (x = 0.08) respectively as compared to BMF, suggesting the evolution of intrinsic feature in the doped samples. Magnetodielectric (MD) effect shows that in the low-frequency regime, the robust MD effect is because of Maxwell-Wagner interfacial polarization, whereas in the high-frequency regime intrinsic effect dominates. Further, magnetoimpedance measurement confirms the presence of substantial intrinsic MD% (~6%) at 1.3 T applied field at 300 K for 4% Mn-doped sample. Finally, the nature and strength of magnetoelectric coupling in BMFM4 and BMFM8 samples at 300 K is found to be biquadratic (P 2 M 2 ) and maximum strength of coupling is 3.09 × 10 −4 emu 2 g −2 and 2.34 × 10 −4 emu 2 g −2 , respectively.