Magnetic order from molecular oxygen anions

PhD ceremony: Mr. S. Riyadi, 11.00 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Magnetic order from molecular oxygen anions

Promotor(s): prof. T.T.M. Palstra, prof. R.A. de Groot

Faculty: Mathematics and Natural Sciences

The magnetic properties of alkali metal oxide compounds, which are determined by the behavior of molecular oxygen species, are investigated with a view to their potential as new spintronics materials.

Spintronics is an emerging technology in which solid-state devices use not only the charge of the electron, but also its spin and the magnetic moment associated with it. Since oxygen is a light element, alkali oxides might offer advantages over materials that are used in today’s technology.

The oxygen molecule (O₂) is important for living creatures. Apart from this, oxygen is also interesting for the condensed-matter physicist because it is a magnetic molecule. Oxygen solidifies below 54.36 K (-218.79 ° C) and shows many interesting physical phenomena below this temperature. For example, it has been reported that oxygen is superconducting below 0.6 K at high pressure (100 GPa).

Different types of oxygen species, oxide (O^2-), peroxide (O₂ ^2-), and superoxide (O₂ ^-), can be formed when molecular oxygen chemically bonds with alkali metals such as potassium (K), rubidium (Rb), and cesium (Cs). These species can give rise to a wide range of interesting physical properties.

The thesis discusses three main topics: 1) exploring the chemical synthesis and properties of new chemical phases of rubidium oxides (RbO_x); 2) ferromagnetic order driven by superoxide ions in RbO_1.66; 3) one-dimensional antiferromagnetic spin-chain order formed by superoxide ions in CsO₂.