Functional Nanomaterials

Recently magnetoelectric nanocomposites are one of the most promising nanofunctional materials.  The nanocompositesconsisting of both ferroelectric (piezoelastic) and ferromagnetic (magnetostrictive) materials are known to exhibit magnetoelectric (ME) effect at room temperature and these composites find applications as magnetic field sensors, transducers and actuators, etc.The interaction between magnetic and electric subsystems through elastic deformations (magnetic-mechanical-electrical interaction) is known as ME effect and its strength is given by the ME voltage coefficient, α_E = δE/Hac, where E is an induced electric field by the application of alternative magnetic field Hac in presence of static magnetic field.

Several investigations in recent years have been reported on piezoelectric-ferrite particulate micro-composites, multilayers, and thin films .However, the information about phase equilibrium, size effects, and structural stability in ME composites were largely unsettled. In comparison to bulk materials, the nanocrystalline materials provide more degrees of freedom, such as lattice strain or interface contacts to optimize the magnitude of properties, viz., magnetization, polarization, strain, and density.

In the present study nanocrystalline BaTiO3 (BT) as piezoelectric phase and nanocrystalline NiFe₂O₄(NF) and Ni_(1-y)Zn_yFe_1.98O_4-δ (NZF) ferrites  as piezomagnetic phases were used to prepare magnetoelectric nanocomposites.

Figures 1(a) and 1(b) show the α_E curves of (100−x)BaTiO₃–(x)NiFe_1.98O₄ (x=20, 40, 60, and 80 wt %) microcomposites and nanocomposites, respectively. The nanocomposites are found to have large α_E values (about five times larger)than their respective microcomposites. The large α_Ein nanocomposites arises from the large piezoelectric coefficient of ferroelectric phase and the large pizomagnetic coefficients of the ferromagnetic phase. On the other hand, an adequate interface contact between the BT and NF phases was observed in the (60)BaTiO₃–(40)NiFe_1.98O₄ nanocomposite from the microscopy studies are in Figure 2(a) and 2(b).

Recently magnetoelectric nanocomposites are one of the most promising nanofunctional materials.  The nanocompositesconsisting of both ferroelectric (piezoelastic) and ferromagnetic (magnetostrictive) materials are known to exhibit magnetoelectric (ME) effect at room temperature and these composites find applications as magnetic field sensors, transducers and actuators, etc.The interaction between magnetic and electric subsystems through elastic deformations (magnetic-mechanical-electrical interaction) is known as ME effect and its strength is given by the ME voltage coefficient, α_E = δE/Hac, where E is an induced electric field by the application of alternative magnetic field Hac in presence of static magnetic field.

Several investigations in recent years have been reported on piezoelectric-ferrite particulate micro-composites, multilayers, and thin films .However, the information about phase equilibrium, size effects, and structural stability in ME composites were largely unsettled. In comparison to bulk materials, the nanocrystalline materials provide more degrees of freedom, such as lattice strain or interface contacts to optimize the magnitude of properties, viz., magnetization, polarization, strain, and density.

In the present study nanocrystalline BaTiO3 (BT) as piezoelectric phase and nanocrystalline NiFe₂O₄(NF) and Ni_(1-y)Zn_yFe_1.98O_4-δ (NZF) ferrites  as piezomagnetic phases were used to prepare magnetoelectric nanocomposites.

Figures 1(a) and 1(b) show the α_E curves of (100−x)BaTiO₃–(x)NiFe_1.98O₄ (x=20, 40, 60, and 80 wt %) microcomposites and nanocomposites, respectively. The nanocomposites are found to have large α_E values (about five times larger)than their respective microcomposites. The large α_Ein nanocomposites arises from the large piezoelectric coefficient of ferroelectric phase and the large pizomagnetic coefficients of the ferromagnetic phase. On the other hand, an adequate interface contact between the BT and NF phases was observed in the (60)BaTiO₃–(40)NiFe_1.98O₄ nanocomposite from the microscopy studies are in Figure 2(a) and 2(b).