EUO

EuO, short for europium(II) oxide, is a binary oxide of europium. It adopts the rock-salt (NaCl-type) crystal structure and typically crystallizes in a cubic lattice with a lattice constant around 5.14 Å at room temperature.

Electronically, EuO is a ferromagnetic semiconductor. The europium ions are in the Eu2+ state (4f7), carrying a large magnetic moment of 7 Bohr moments per ion. It orders ferromagnetically below a Curie temperature of about 69 K in stoichiometric bulk form. The 4f states are localized, while the conduction band is derived from Eu 5d/6s states; the exchange between localized moments and conduction electrons leads to a spin-split conduction band and a relatively narrow optical band gap of roughly 1–2 eV.

Stoichiometric EuO is sensitive to oxidation; exposure to air can convert Eu2+ to Eu3+ and form higher oxides such as Eu2O3, so synthesis and handling are typically done under reducing or inert conditions.

Non-stoichiometric EuO1−x (with oxygen vacancies) or doped EuO (for example with Gd) exhibit increased carrier concentration and can show enhanced ferromagnetism, and in thin films Tc can be raised relative to bulk.

Applications include spintronic devices where EuO acts as a spin-filter barrier in magnetic tunnel junctions and potentially as a magneto-optical material.

See also: EuS.