The paper first introduces the basic physics behind perovskite multiferroics. Then the recent progress on simple, complex perovskites, and manganites are briefly reviewed. The review discloses two important directions on achievement multiferrocity in perovskite: pay with strain engineering and adjust octahedral deformation. The authors also suggest that specific issues like leakage current and characterization platforms are also very important for the study of multiferroics.

A brief review on perovskite multiferroics

Extending the framework for multiferroic materials, in which long-range electric and magnetic orderings coexist, we present a novel 'multiglass' concept, where two different glassy states occur simultaneously. It applies to Sr0.98Mn0.02TiO3 ceramics, where the Mn2+ dopant ions are at the origin of both polar and spin glasses. Spin freezing is initiated at the dipolar glass temperature, Tg≈38 K. Below Tg, both glass phases are independently verified by memory and rejuvenation effects. Strong biquadratic interaction of the Mn2+ spins with the optic soft mode of the incipient ferroelectric host crystal SrTiO3 explains the high spin glass temperature and comparably strong higher order magnetoelectric coupling between the polar and magnetic degrees of freedom.

https://iopscience.iop.org/article/10.1088/0953-8984/20/43/434216/pdf

(Sr,Mn)TiO3—a magnetoelectrically coupled multiglass

The magnetic and electric static and dynamic properties of hexagonal multiferroic RMnO3 are studied based on the transverse Ising and Heisenberg models using a Green’s function technique. The influence of the magnetoelectric coupling and the exchange interaction constants is discussed. The coexistence of ferroelectricity and magnetism leads to interplay between the electric and magnetic properties which was found as an anomaly, as a kink in the temperature dependence of different static and dynamic properties in the vicinity of the magnetic phase transition temperature TN. The spin excitations show a novel softening around TN due to the magnetoelectric coupling. The magnetic-field-induced polarization is investigated. The obtained results are in qualitative agreement with the experimental data.

Static and dynamic properties of hexagonal multiferroic RMnO3 compounds

We report remarkable results due to the coupling between the magnetization and the electric field induced polarization in EuTiO3. Using a microscopic model Hamiltonian to describe the three coupled sublattices, Eu-(spin-up), Eu-(spin-down), and Ti-(moment), the spin flop and spin reorientation phase transitions were described with and without the electric-magnetic coupling interaction. The external electric field can be used to tune the temperature of the spin reorientation phase transition TSR = TSR(E). When the TSR is tuned around the EuTiO3—Neel temperature (TN = 5.5 K), an outstanding effect emerges in which EuTiO3 releases heat under magnetic field change. The electric field controlling the spin reorientation transition and the endo-exothermic processes are discussed through the microscopic interactions model parameters.

Electric field triggering the spin reorientation and controlling the absorption and release of heat in the induced multiferroic compound EuTiO3

Magnetoelectricity in multiferroically composed multilayers and multiglasses

EuTiO3 is a quantum paraelectric as well as an antiferromagnet. The most attractive property for EuTiO3 is the magnetoelectric coupling effect. In the present work, we investigate the influence of the external fields on EuTiO3, including the electric field E and magnetic field h. The application of the electric field counteracts the quantum fluctuation and forces the system into an electrically ordered state. The applied magnetic field directly induces the fluctuation of the spin-pair correlation and indirectly influences the dielectric behaviors through the magnetoelectric coupling. In addition, we notice that the contribution of the magnetic field depends closely on the temperature condition and the electric field background. The (p, h, E, T) and (e, h, T) diagrams are presented showing the temperature, magnetic and electric field dependence of the polarization and the dielectric capacitance. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

S. J. Gong

Papers

Magnetic-field-induced polarization and magnetocapacitance in quantum paraelectric EuTiO3