Multiferroic magnetoelectric fluorides: why are there so many magnetic ferroelectrics?

Abstract

We review work on multiferroic magnetic fluorides with an aim to correct the popular opinion that magnetic ferroelectrics are rare in nature. After a qualitative summary describing the main families of magnetic fluorides that are piezoelectric and probably ferroelectric, we discuss in detail the most popular recent groups, namely the K(3)Fe(5)F(15) and Pb(5)Cr(3)F(19) families.

Phase transition and enhanced magneto-dielectric response in BiFeO3-DyMnO3 multiferroics

“…[1][2][3][4][5][6][7][8][9][10][11] An essential feature of a multiferroic system is the presence of magnetoelectric (ME) coupling (not all multiferroics are magnetoelectric, e.g., BaCoF 4 ) which permits a mutual control between ferroic order parameters (i.e., electric and magnetic ordering). 2,11 Multiferroics are very rare in nature due to the chemical incompatibility and mutual exclusiveness of ferroelectric and ferromagnetic ordering in many oxides, more common among fluorides. 3,11 In this context, BiFeO 3 (BFO) with a distorted perovskite ABO 3 structure is a proto-type multiferroic material owing to its high ferroelectric transition temperature (T C % 830 C) and antiferromagnetic (AFM) Neel temperature (T N % 370 C).…”

“…2,11 Multiferroics are very rare in nature due to the chemical incompatibility and mutual exclusiveness of ferroelectric and ferromagnetic ordering in many oxides, more common among fluorides. 3,11 In this context, BiFeO 3 (BFO) with a distorted perovskite ABO 3 structure is a proto-type multiferroic material owing to its high ferroelectric transition temperature (T C % 830 C) and antiferromagnetic (AFM) Neel temperature (T N % 370 C). 4 The ferroelectricity in BFO is caused by the Bi 6s lone pair electrons, while spin of transition metal cation Fe 3þ is responsible for G-type antiferromagnetic ordering with a long range spin cycloid with period of 620-640 Å .…”

“…2 The spiral spin structure can be suppressed or destroyed by suitable chemical substitution, fabrication of solid solutions, preparation of nano particles less than the size of the spin cycloid, application of high magnetic fields, and growing epitaxial thin film. [7][8][9][10][11][12][13] BFO forms solid solutions with perovskite (ABO 3 ) and rare earth manganites (REMnO 3 ) over a wide compositional range and possess different structural symmetries which display intriguing multiferroic properties. 2,9,12 REMnO 3 exhibits two distinct crystal structures depending on the ionic radius of the RE ions.…”

Multiferroic BaCoF4 in Thin Film Form: Ferroelectricity, Magnetic Ordering, and Strain

“…To date, the majority of studies on multiferroic materials have been devoted to oxide perovskites in the form ABO 3 . The conventional ion transfer ferroelectricity mechanism in oxide perovskites is known to rely on the covalent bonds between oxygen and B-site cations with closed-shell, non-magnetic electronic configurations.…”

“…3 The best known example is the BaMF 4 compound, where M=Mn, Fe, Co, or Ni. Recent theoretical studies 4,5 focused on their magnetoelectric and multiferroic properties.…”