Multiferroic materials, which show simultaneous ferroelectric and magnetic ordering, exhibit unusual physical properties — and in turn promise new device applications — as a result of the coupling between their dual order parameters. We review recent progress in the growth, characterization and understanding of thin-film multiferroics. The availability of high-quality thin-film multiferroics makes it easier to tailor their properties through epitaxial strain, atomic-level engineering of chemistry and interfacial coupling, and is a prerequisite for their incorporation into practical devices. We discuss novel device paradigms based on magnetoelectric coupling, and outline the key scientific challenges in the field.

Multiferroics: progress and prospects in thin films.

Multiferroic magnetoelectric materials, which simultaneously exhibit ferroelectricity and ferromagnetism, have recently stimulated a sharply increasing number of research activities for their scientific interest and significant technological promise in the novel multifunctional devices. Natural multiferroic single-phase compounds are rare, and their magnetoelectric responses are either relatively weak or occurs at temperatures too low for practical applications. In contrast, multiferroic composites, which incorporate both ferroelectric and ferri-/ferromagnetic phases, typically yield giant magnetoelectric coupling response above room temperature, which makes them ready for technological applications. This review of mostly recent activities begins with a brief summary of the historical perspective of the multiferroic magnetoelectric composites since its appearance in 1972. In such composites the magnetoelectric effect is generated as a product property of a magnetostrictive and a piezoelectric substance. A...

Multiferroic magnetoelectric composites: Historical perspective, status, and future directions

Multiferroic magnetoelectrics are materials that are both ferromagnetic and ferroelectric in the same phase. As a result, they have a spontaneous magnetization that can be switched by an applied magnetic field, a spontaneous polarization that can be switched by an applied electric field, and often some coupling between the two. Very few exist in nature or have been synthesized in the laboratory. In this paper, we explore the fundamental physics behind the scarcity of ferromagnetic ferroelectric coexistence. In addition, we examine the properties of some known magnetically ordered ferroelectric materials. We find that, in general, the transition metal d electrons, which are essential for magnetism, reduce the tendency for off-center ferroelectric distortion. Consequently, an additional electronic or structural driving force must be present for ferromagnetism and ferroelectricity to occur simultaneously.

Why Are There so Few Magnetic Ferroelectrics

Metal Oxides and Oxysalts as Anode Materials for Li Ion Batteries

Oxide pyrochlores — A review

Charge-ordered phases of rare earth manganates are novel manifestations arising from interactions between the charge carriers and phonons, giving rise to the localization of carriers at specific sites in the lattice below a certain temperature. Accompanying this phenomenon, the Mn 3+ (e g ) orbitals and the associated lattice distortions also exhibit long range ordering (orbital ordering). What makes the manganates even more interesting is the occurrence of complex spin ordering related to anisotropic magnetic interactions. In this article, we discuss the emerging scenario of charge-ordered rare earth manganates in the light of specific case studies and highlight some of the new experimental findings related to spin, orbital and charge ordering. We also examine features such as the charge stripes and phase separation found experimentally in these materials, and discuss the factors that affect charge-ordering such as the size of A-site cations and magnetic and electric fields, as well as isotopic and chemical substitutions.

http://iopscience.iop.org/article/10.1088/0953-8984/12/7/201/pdf

Charge ordering in the rare earth manganates: the experimental situation

Manganites with the perovskite structure represent a very important family of oxides which are extensively studied for their colossal magnetoresistance (CMR) properties In the present review we discuss the different factors which govern the magnetic and transport properties of these materials: carrier concentration, average size of the interpolated cation, and mismatch effect on the A-site Three types of oxides are mainly examined:  (i) the hole doped manganites Ln07A03MnO3 (A = Ca, Sr, Ba), (ii) the “charge ordered” Ln05A05MnO3 manganites, and (iii) the electron doped manganites Ca1-xLnxMnO3 and Ca1-xThxMnO3 The relationships between structural and magnetic transitions are discussed, and particular attention is paid to charge ordering phenomena The doping of the Mn sites by various elements (Al, Ga, In, Ti, Sn, Fe, Cr, Co, Ni) is systematically examined The beneficial effect of “Cr, Co, Ni” elements, which induce CMR properties in these perovskites, is emphasized

Colossal Magnetoresistance Manganite Perovskites: Relations between Crystal Chemistry and Properties

AILaNb2O7: A new series of layered perovskites exhibiting ion exchange and intercalation behaviour

Oxygen defect K2NiF4-type oxides: The compounds La2−xSrxCuO4−x2+δ

Three new perovskites in the LaBaMn2O6-x family have been synthesized by controlling the oxygen pressure, during both synthesis and postannealing. Structural determination from powder neutron diffraction (PND) data shows that one form of LaBaMn2O6 is cubic (a = 3.906 A), with a disordered distribution of La3+ and Ba2+ cations, whereas a second form of LaBaMn2O6 is tetragonal (a = 3.916 A; c = 7.805 A), with an alternate stacking of lanthanum and barium layers along c. The same La/Ba cation order is observed for the ordered, oxygen-deficient perovskite LaBaMn2O5, which is also tetragonal (a = 5.650 A; c = 7.808 A) and adopts a YBaCuFeO5-related structure. Elucidation of the magnetic structure of LaBaMn2O5, from low-temperature PND data, leads to a G-type antiferromagnetic model; the superimposed Mn2+/Mn3+ charge order results in ferrimagnetic behavior for this phase and explains its magnetic properties, as obtained from susceptibility measurements. In both forms of LaBaMn2O6, the PND data show a ferromagne...

Bernard Raveau

Papers

Charge ordering in the rare earth manganates: the experimental situation

Colossal Magnetoresistance Manganite Perovskites: Relations between Crystal Chemistry and Properties

AILaNb2O7: A new series of layered perovskites exhibiting ion exchange and intercalation behaviour

Oxygen defect K2NiF4-type oxides: The compounds La2−xSrxCuO4−x2+δ

Order-disorder phenomena in new LaBaMn2O6-x CMR perovskites. Crystal and magnetic structure