Strain assisted magnetoelectric coupling in ordered nanomagnets of CoFe2O4/SrRuO3/(Pb(Mg1/3Nb2/3)O3-PbTiO3) heterostructures.

We have explored the electric field controlled magnetization in the nanodot CoFe2O4/SrRuO3/PMN-PT (CFO/SRO/PMN-PT) heterostructures. Ordered ferromagnetic CFO nanodots (∼300 nm lateral dimension) are developed on the PMN-PT substrate (ferroelectric as well as piezoelectric) using a nanostencil-mask pattering method during pulsed laser deposition. The nanostructures reveal electric field induced magnetization reversal in the single domain CFO nanodots through transfer of piezostrains from the piezoelectric PMN-PT substrate to the CFO. Further, electric field modulated spin structure of CFO nanomagnets is analyzed by using x-ray magnetic circular dichroism (XMCD). The XMCD analysis reveals cations (Fe3+/Co2+) redistribution on the octahedral and tetrahedral site in the electric field poled CFO nanodots, establishing the strain induced magneto-electric coupling effects. The CFO/SRO/PMN-PT nanodots structure demonstrate multilevel switching of ME coupling coefficient (α) by applying selective positive and negative electric fields in a non-volatile manner. The retention of two stable states ofαis illustrated for ∼106seconds, which can be employed to store the digital data in non-volatile memory devices. Thus the voltage controlled magnetization in the nanodot structures leads a path towards the invention of energy efficient high-density memory devices.

Spin reorientation transition and coupled spin-lattice dynamics of Sm0.6Dy0.4FeO3.

In this work, we have presented a solid-solution of Sm0.6Dy0.4FeO3 in the form of nano-particles having spin reorientation transition (SRT) at a temperature interval of 220-260 K. The lattice dynamics of Sm0.6Dy0.4FeO3 have investigated by temperature-dependent x-ray diffraction and Raman spectroscopy. A negative thermal expansion at low temperatures has observed, which might be due to the interaction between Sm3+ and Fe3+ sublattice. Anomalous behavior in lattice parameters, octahedral tilt angle, and bond lengths have observed in the vicinity of SRT, which confirms the existence of magneto-elastic coupling in the system. The strong anomaly has observed in linewidth and phonon frequencies of Raman modes around SRT, which may be related to the spin-phonon coupling in Sm0.6Dy0.4FeO3. The contribution of SRT in lattice change and the presence of spin-phonon coupling can help to understand the correlation between the magnetic and structural properties of orthoferrite.