page_title: Multiferroics
section_title: History
hierarchical_section_title: Multiferroics / History
caption_attribution_description: English: Bar chart showing number of papers using the keyword terms magnetoelectric and multiferroic. Data collected via standard Web of Science search for magneto-electric, magnetoelectric, multi-ferroic, and multiferroic.
context_page_description: Multiferroics are defined as materials that exhibit more than one of the primary ferroic properties in the same phase:
  ferromagnetism — a magnetisation that is switchable by an applied magnetic field
  ferroelectricity — an electric polarisation that is switchable by an applied electric field
  ferroelasticity — a deformation that is switchable by an applied stress
  While ferroelectric ferroelastics and ferromagnetic ferroelastics are formally multiferroics, these days the term is usually used to describe the magnetoelectric multiferroics that are simultaneously ferromagnetic and ferroelectric. Sometimes the definition is expanded to include non-primary order parameters, such as antiferromagnetism or ferrimagnetism. In addition, other types of primary order, such as ferroic arrangements of magneotelectric multipoles of which ferrotoroidicity is an example, have also been recently proposed.
  Besides scientific interest in their physical properties, multiferroics have potential for applications as actuators, switches, magnetic field sensors and new types of electronic memory devices.
context_section_description: A Web of Science search for the term multiferroic yields the year 2000 paper "Why are there so few magnetic ferroelectrics?" from N. A. Spaldin (then Hill) as the earliest result. This work explained the origin of the contraindication between magnetism and ferroelectricity and proposed practical routes to circumvent it, and is widely credited with starting the modern explosion of interest in multiferroic materials . The availability of practical routes to creating multiferroic materials from 2000 stimulated intense activity. Particularly key early works were the discovery of large ferroelectric polarization in epitaxially grown thin films of magnetic BiFeO₃, the observation that the non-collinear magnetic ordering in orthorhombic TbMnO₃ and TbMn₂O₅ causes ferroelectricity, and the identification of unusual improper ferroelectricity that is compatible with the coexistence of magnetism in hexagonal manganite YMnO₃. The graph to the right shows in red the number of papers on multiferroics from a Web of Science search until 2008; the exponential increase continues today.
caption: History of multiferroics: number of papers per year on magnetoelectrics or the magnetoelectric effect (in blue), and on multiferroics (in red)
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